Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$148.91	7.835%	$160.5771	$160.58	$160.60	$160.60
Purchase #2	$175.57	11.288%	$195.3883	$195.39	$195.40	$195.40
Purchase #3	$229.33	11.576%	$255.8772	$255.88	$255.90	$255.90
Purchase #4	$234.46	13.558%	$266.2481	$266.25	$266.25	$266.20
Purchase #5	$119.46	10.166%	$131.6043	$131.60	$131.60	$131.60
Purchase #6	$244.69	7.125%	$262.1242	$262.12	$262.10	$262.10
Purchase #7	$120.47	10.815%	$133.4988	$133.50	$133.50	$133.50
7 purchase totals =	$1,272.89		$1,405.3180	$1,405.32	$1,405.35	$1,405.30