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	$179.79	3.250%	$185.6332	$185.63	$185.65	$185.60
Purchase #2	$224.87	4.335%	$234.6181	$234.62	$234.60	$234.60
Purchase #3	$110.49	5.193%	$116.2277	$116.23	$116.25	$116.20
Purchase #4	$159.41	11.174%	$177.2225	$177.22	$177.20	$177.20
Purchase #5	$32.66	3.510%	$33.8064	$33.81	$33.80	$33.80
Purchase #6	$64.39	11.148%	$71.5682	$71.57	$71.55	$71.60
Purchase #7	$214.64	13.143%	$242.8501	$242.85	$242.85	$242.90
7 purchase totals =	$986.25		$1,061.9262	$1,061.93	$1,061.90	$1,061.90