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	$42.71	7.455%	$45.894	$45.89	$45.90	$45.90
Purchase #2	$159.84	13.578%	$181.5431	$181.54	$181.55	$181.50
Purchase #3	$96.29	12.236%	$108.072	$108.07	$108.05	$108.10
Purchase #4	$19.73	13.689%	$22.4308	$22.43	$22.45	$22.40
Purchase #5	$176.48	11.492%	$196.7611	$196.76	$196.75	$196.80
Purchase #6	$184.73	11.851%	$206.6224	$206.62	$206.60	$206.60
Purchase #7	$35.39	11.681%	$39.5239	$39.52	$39.50	$39.50
7 purchase totals =	$715.17		$800.8473	$800.83	$800.80	$800.80