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	$48.30	10.366%	$53.3068	$53.31	$53.30	$53.30
Purchase #2	$88.25	4.589%	$92.2998	$92.30	$92.30	$92.30
Purchase #3	$40.89	12.438%	$45.9759	$45.98	$46.00	$46.00
Purchase #4	$90.99	9.289%	$99.4421	$99.44	$99.45	$99.40
Purchase #5	$113.56	12.274%	$127.4984	$127.50	$127.50	$127.50
Purchase #6	$112.68	7.873%	$121.5513	$121.55	$121.55	$121.60
Purchase #7	$135.53	4.576%	$141.7319	$141.73	$141.75	$141.70
7 purchase totals =	$630.20		$681.8062	$681.81	$681.85	$681.80