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	$149.42	5.540%	$157.6979	$157.70	$157.70	$157.70
Purchase #2	$128.76	6.781%	$137.4912	$137.49	$137.50	$137.50
Purchase #3	$80.43	4.167%	$83.7815	$83.78	$83.80	$83.80
Purchase #4	$72.52	11.587%	$80.9229	$80.92	$80.90	$80.90
Purchase #5	$122.59	6.500%	$130.5584	$130.56	$130.55	$130.60
Purchase #6	$157.38	7.179%	$168.6783	$168.68	$168.70	$168.70
Purchase #7	$233.69	12.671%	$263.3009	$263.30	$263.30	$263.30
7 purchase totals =	$944.79		$1,022.4311	$1,022.43	$1,022.45	$1,022.50