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	$95.67	5.126%	$100.574	$100.57	$100.55	$100.60
Purchase #2	$59.91	4.825%	$62.8007	$62.80	$62.80	$62.80
Purchase #3	$158.51	13.230%	$179.4809	$179.48	$179.50	$179.50
Purchase #4	$39.91	9.168%	$43.5689	$43.57	$43.55	$43.60
Purchase #5	$174.32	11.169%	$193.7898	$193.79	$193.80	$193.80
Purchase #6	$89.28	4.316%	$93.1333	$93.13	$93.15	$93.10
Purchase #7	$63.83	11.867%	$71.4047	$71.40	$71.40	$71.40
7 purchase totals =	$681.43		$744.7523	$744.74	$744.75	$744.80