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	$131.43	13.309%	$148.922	$148.92	$148.90	$148.90
Purchase #2	$99.29	8.694%	$107.9223	$107.92	$107.90	$107.90
Purchase #3	$199.64	9.710%	$219.025	$219.03	$219.05	$219.00
Purchase #4	$34.66	3.626%	$35.9168	$35.92	$35.90	$35.90
Purchase #5	$235.63	12.266%	$264.5324	$264.53	$264.55	$264.50
Purchase #6	$154.48	7.533%	$166.117	$166.12	$166.10	$166.10
Purchase #7	$131.72	9.622%	$144.3941	$144.39	$144.40	$144.40
7 purchase totals =	$986.85		$1,086.8296	$1,086.83	$1,086.80	$1,086.70