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	$33.82	3.148%	$34.8847	$34.88	$34.90	$34.90
Purchase #2	$242.47	4.130%	$252.484	$252.48	$252.50	$252.50
Purchase #3	$80.37	11.654%	$89.7363	$89.74	$89.75	$89.70
Purchase #4	$137.33	9.822%	$150.8186	$150.82	$150.80	$150.80
Purchase #5	$78.99	9.272%	$86.314	$86.31	$86.30	$86.30
Purchase #6	$106.86	3.823%	$110.9453	$110.95	$110.95	$110.90
Purchase #7	$175.89	4.208%	$183.2915	$183.29	$183.30	$183.30
7 purchase totals =	$855.73		$908.4744	$908.47	$908.50	$908.40