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	$23.52	4.563%	$24.5932	$24.59	$24.60	$24.60
Purchase #2	$171.45	5.471%	$180.83	$180.83	$180.85	$180.80
Purchase #3	$166.33	4.696%	$174.1409	$174.14	$174.15	$174.10
Purchase #4	$110.47	7.153%	$118.3719	$118.37	$118.35	$118.40
Purchase #5	$52.56	5.231%	$55.3094	$55.31	$55.30	$55.30
Purchase #6	$149.76	3.292%	$154.6901	$154.69	$154.70	$154.70
Purchase #7	$233.43	13.761%	$265.5523	$265.55	$265.55	$265.60
7 purchase totals =	$907.52		$973.4878	$973.48	$973.50	$973.50