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	$245.95	4.471%	$256.9464	$256.95	$256.95	$256.90
Purchase #2	$134.75	9.621%	$147.7143	$147.71	$147.70	$147.70
Purchase #3	$95.27	4.224%	$99.2942	$99.29	$99.30	$99.30
Purchase #4	$53.61	6.579%	$57.137	$57.14	$57.15	$57.10
Purchase #5	$168.38	13.760%	$191.5491	$191.55	$191.55	$191.50
Purchase #6	$15.77	3.288%	$16.2885	$16.29	$16.30	$16.30
Purchase #7	$94.88	5.653%	$100.2436	$100.24	$100.25	$100.20
7 purchase totals =	$808.61		$869.1731	$869.17	$869.20	$869.00