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	$119.70	7.626%	$128.8283	$128.83	$128.85	$128.80
Purchase #2	$57.55	12.550%	$64.7725	$64.77	$64.75	$64.80
Purchase #3	$84.95	5.711%	$89.8015	$89.80	$89.80	$89.80
Purchase #4	$82.48	7.357%	$88.5481	$88.55	$88.55	$88.50
Purchase #5	$241.85	11.665%	$270.0618	$270.06	$270.05	$270.10
Purchase #6	$204.74	12.409%	$230.1462	$230.15	$230.15	$230.10
Purchase #7	$146.33	3.767%	$151.8423	$151.84	$151.85	$151.80
7 purchase totals =	$937.60		$1,024.0007	$1,024.00	$1,024.00	$1,023.90