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	$188.26	3.127%	$194.1469	$194.15	$194.15	$194.10
Purchase #2	$73.73	11.329%	$82.0829	$82.08	$82.10	$82.10
Purchase #3	$111.77	8.145%	$120.8737	$120.87	$120.85	$120.90
Purchase #4	$121.70	4.218%	$126.8333	$126.83	$126.85	$126.80
Purchase #5	$110.66	5.787%	$117.0639	$117.06	$117.05	$117.10
Purchase #6	$244.50	7.343%	$262.4536	$262.45	$262.45	$262.50
Purchase #7	$71.26	9.552%	$78.0668	$78.07	$78.05	$78.10
7 purchase totals =	$921.88		$981.5211	$981.51	$981.50	$981.60