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	$190.73	10.227%	$210.236	$210.24	$210.25	$210.20
Purchase #2	$223.86	11.684%	$250.0158	$250.02	$250.00	$250.00
Purchase #3	$198.30	12.244%	$222.5799	$222.58	$222.60	$222.60
Purchase #4	$77.77	6.112%	$82.5233	$82.52	$82.50	$82.50
Purchase #5	$118.67	10.863%	$131.5611	$131.56	$131.55	$131.60
Purchase #6	$160.31	9.574%	$175.6581	$175.66	$175.65	$175.70
Purchase #7	$29.92	8.467%	$32.4533	$32.45	$32.45	$32.50
7 purchase totals =	$999.56		$1,105.0275	$1,105.03	$1,105.00	$1,105.10