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	$149.93	4.286%	$156.356	$156.36	$156.35	$156.40
Purchase #2	$144.85	5.320%	$152.556	$152.56	$152.55	$152.60
Purchase #3	$233.43	7.290%	$250.447	$250.45	$250.45	$250.40
Purchase #4	$186.39	13.572%	$211.6869	$211.69	$211.70	$211.70
Purchase #5	$221.83	9.593%	$243.1102	$243.11	$243.10	$243.10
Purchase #6	$140.89	5.492%	$148.6277	$148.63	$148.65	$148.60
Purchase #7	$205.32	13.653%	$233.3523	$233.35	$233.35	$233.40
7 purchase totals =	$1,282.64		$1,396.1361	$1,396.15	$1,396.15	$1,396.20