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	$193.40	3.444%	$200.0607	$200.06	$200.05	$200.10
Purchase #2	$63.35	13.309%	$71.7813	$71.78	$71.80	$71.80
Purchase #3	$103.62	7.645%	$111.5417	$111.54	$111.55	$111.50
Purchase #4	$64.57	8.640%	$70.1488	$70.15	$70.15	$70.10
Purchase #5	$102.92	10.632%	$113.8625	$113.86	$113.85	$113.90
Purchase #6	$101.95	6.613%	$108.692	$108.69	$108.70	$108.70
Purchase #7	$120.43	10.872%	$133.5231	$133.52	$133.50	$133.50
7 purchase totals =	$750.24		$809.6101	$809.60	$809.60	$809.60