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	$64.84	4.700%	$67.8875	$67.89	$67.90	$67.90
Purchase #2	$67.66	12.810%	$76.3272	$76.33	$76.35	$76.30
Purchase #3	$43.68	6.591%	$46.5589	$46.56	$46.55	$46.60
Purchase #4	$99.56	11.502%	$111.0114	$111.01	$111.00	$111.00
Purchase #5	$10.87	9.331%	$11.8843	$11.88	$11.90	$11.90
Purchase #6	$28.88	5.381%	$30.434	$30.43	$30.45	$30.40
Purchase #7	$46.76	3.210%	$48.261	$48.26	$48.25	$48.30
7 purchase totals =	$362.25		$392.3643	$392.36	$392.40	$392.40