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	$150.51	11.450%	$167.7434	$167.74	$167.75	$167.70
Purchase #2	$62.72	4.788%	$65.723	$65.72	$65.70	$65.70
Purchase #3	$181.60	12.561%	$204.4108	$204.41	$204.40	$204.40
Purchase #4	$221.39	3.671%	$229.5172	$229.52	$229.50	$229.50
Purchase #5	$55.66	10.563%	$61.5394	$61.54	$61.55	$61.50
Purchase #6	$120.66	3.468%	$124.8445	$124.84	$124.85	$124.80
Purchase #7	$139.68	9.809%	$153.3812	$153.38	$153.40	$153.40
7 purchase totals =	$932.22		$1,007.1595	$1,007.15	$1,007.15	$1,007.00