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	$91.68	9.627%	$100.506	$100.51	$100.50	$100.50
Purchase #2	$176.91	12.564%	$199.137	$199.14	$199.15	$199.10
Purchase #3	$193.48	3.431%	$200.1183	$200.12	$200.10	$200.10
Purchase #4	$241.97	9.144%	$264.0957	$264.10	$264.10	$264.10
Purchase #5	$168.98	9.684%	$185.344	$185.34	$185.35	$185.30
Purchase #6	$84.66	4.718%	$88.6543	$88.65	$88.65	$88.70
Purchase #7	$39.77	8.872%	$43.2984	$43.30	$43.30	$43.30
7 purchase totals =	$997.45		$1,081.1537	$1,081.16	$1,081.15	$1,081.10