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	$155.52	11.857%	$173.96	$173.96	$173.95	$174.00
Purchase #2	$111.68	10.590%	$123.5069	$123.51	$123.50	$123.50
Purchase #3	$188.88	12.575%	$212.6317	$212.63	$212.65	$212.60
Purchase #4	$99.27	6.303%	$105.527	$105.53	$105.55	$105.50
Purchase #5	$50.66	5.550%	$53.4716	$53.47	$53.45	$53.50
Purchase #6	$211.32	10.861%	$234.2715	$234.27	$234.25	$234.30
Purchase #7	$149.44	5.378%	$157.4769	$157.48	$157.50	$157.50
7 purchase totals =	$966.77		$1,060.8456	$1,060.85	$1,060.85	$1,060.90