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	$92.58	10.747%	$102.5296	$102.53	$102.55	$102.50
Purchase #2	$193.26	9.207%	$211.0534	$211.05	$211.05	$211.10
Purchase #3	$190.32	6.727%	$203.1228	$203.12	$203.10	$203.10
Purchase #4	$181.89	5.185%	$191.321	$191.32	$191.30	$191.30
Purchase #5	$73.88	6.467%	$78.6578	$78.66	$78.65	$78.70
Purchase #6	$100.75	7.806%	$108.6145	$108.61	$108.60	$108.60
Purchase #7	$243.63	13.641%	$276.8636	$276.86	$276.85	$276.90
7 purchase totals =	$1,076.31		$1,172.1627	$1,172.15	$1,172.10	$1,172.20