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	$164.59	5.144%	$173.0565	$173.06	$173.05	$173.10
Purchase #2	$126.26	13.186%	$142.9086	$142.91	$142.90	$142.90
Purchase #3	$138.51	13.650%	$157.4166	$157.42	$157.40	$157.40
Purchase #4	$42.35	3.258%	$43.7298	$43.73	$43.75	$43.70
Purchase #5	$209.64	4.137%	$218.3128	$218.31	$218.30	$218.30
Purchase #6	$63.98	13.661%	$72.7203	$72.72	$72.70	$72.70
Purchase #7	$130.59	4.707%	$136.7369	$136.74	$136.75	$136.70
7 purchase totals =	$875.92		$944.8815	$944.89	$944.85	$944.80