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	$147.63	4.485%	$154.2512	$154.25	$154.25	$154.30
Purchase #2	$127.72	11.557%	$142.4806	$142.48	$142.50	$142.50
Purchase #3	$145.73	8.428%	$158.0121	$158.01	$158.00	$158.00
Purchase #4	$194.70	13.159%	$220.3206	$220.32	$220.30	$220.30
Purchase #5	$61.57	10.794%	$68.2159	$68.22	$68.20	$68.20
Purchase #6	$48.30	11.571%	$53.8888	$53.89	$53.90	$53.90
Purchase #7	$189.35	12.240%	$212.5264	$212.53	$212.55	$212.50
7 purchase totals =	$915.00		$1,009.6956	$1,009.70	$1,009.70	$1,009.70