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	$247.52	4.658%	$259.0495	$259.05	$259.05	$259.00
Purchase #2	$20.55	11.198%	$22.8512	$22.85	$22.85	$22.90
Purchase #3	$102.60	8.363%	$111.1804	$111.18	$111.20	$111.20
Purchase #4	$236.36	5.839%	$250.1611	$250.16	$250.15	$250.20
Purchase #5	$99.72	11.461%	$111.1489	$111.15	$111.15	$111.10
Purchase #6	$139.53	9.614%	$152.9444	$152.94	$152.95	$152.90
Purchase #7	$131.50	9.297%	$143.7256	$143.73	$143.75	$143.70
7 purchase totals =	$977.78		$1,051.0611	$1,051.06	$1,051.10	$1,051.00