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	$111.94	11.456%	$124.7638	$124.76	$124.75	$124.80
Purchase #2	$86.48	4.254%	$90.1589	$90.16	$90.15	$90.20
Purchase #3	$118.44	4.476%	$123.7414	$123.74	$123.75	$123.70
Purchase #4	$41.68	4.606%	$43.5998	$43.60	$43.60	$43.60
Purchase #5	$156.94	13.563%	$178.2258	$178.23	$178.25	$178.20
Purchase #6	$131.95	4.679%	$138.1239	$138.12	$138.10	$138.10
Purchase #7	$195.51	10.236%	$215.5224	$215.52	$215.50	$215.50
7 purchase totals =	$842.94		$914.1360	$914.13	$914.10	$914.10