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	$121.56	9.871%	$133.5592	$133.56	$133.55	$133.60
Purchase #2	$114.66	11.556%	$127.9101	$127.91	$127.90	$127.90
Purchase #3	$226.88	3.374%	$234.5349	$234.53	$234.55	$234.50
Purchase #4	$90.66	3.753%	$94.0625	$94.06	$94.05	$94.10
Purchase #5	$93.82	6.363%	$99.7898	$99.79	$99.80	$99.80
Purchase #6	$177.57	5.714%	$187.7163	$187.72	$187.70	$187.70
Purchase #7	$136.56	8.162%	$147.706	$147.71	$147.70	$147.70
7 purchase totals =	$961.71		$1,025.2788	$1,025.28	$1,025.25	$1,025.30