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	$56.33	5.464%	$59.4079	$59.41	$59.40	$59.40
Purchase #2	$173.89	3.198%	$179.451	$179.45	$179.45	$179.50
Purchase #3	$190.51	10.488%	$210.4907	$210.49	$210.50	$210.50
Purchase #4	$249.42	13.505%	$283.1042	$283.10	$283.10	$283.10
Purchase #5	$60.25	7.272%	$64.6314	$64.63	$64.65	$64.60
Purchase #6	$170.55	9.440%	$186.6499	$186.65	$186.65	$186.60
Purchase #7	$33.32	10.119%	$36.6917	$36.69	$36.70	$36.70
7 purchase totals =	$934.27		$1,020.4268	$1,020.42	$1,020.45	$1,020.40