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	$241.85	4.589%	$252.9485	$252.95	$252.95	$252.90
Purchase #2	$242.35	11.479%	$270.1694	$270.17	$270.15	$270.20
Purchase #3	$150.95	6.195%	$160.3014	$160.30	$160.30	$160.30
Purchase #4	$79.81	3.841%	$82.8755	$82.88	$82.90	$82.90
Purchase #5	$249.62	5.854%	$264.2328	$264.23	$264.25	$264.20
Purchase #6	$216.40	11.253%	$240.7515	$240.75	$240.75	$240.80
Purchase #7	$211.83	8.404%	$229.6322	$229.63	$229.65	$229.60
7 purchase totals =	$1,392.81		$1,500.9113	$1,500.91	$1,500.95	$1,500.90