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	$200.41	3.554%	$207.5326	$207.53	$207.55	$207.50
Purchase #2	$87.94	9.417%	$96.2213	$96.22	$96.20	$96.20
Purchase #3	$18.82	9.743%	$20.6536	$20.65	$20.65	$20.70
Purchase #4	$67.69	7.700%	$72.9021	$72.90	$72.90	$72.90
Purchase #5	$43.82	9.770%	$48.1012	$48.10	$48.10	$48.10
Purchase #6	$138.98	10.740%	$153.9065	$153.91	$153.90	$153.90
Purchase #7	$136.74	11.594%	$152.5936	$152.59	$152.60	$152.60
7 purchase totals =	$694.40		$751.9109	$751.90	$751.90	$751.90