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	$61.40	8.803%	$66.805	$66.81	$66.80	$66.80
Purchase #2	$55.61	10.352%	$61.3667	$61.37	$61.35	$61.40
Purchase #3	$231.91	3.654%	$240.384	$240.38	$240.40	$240.40
Purchase #4	$132.33	12.411%	$148.7535	$148.75	$148.75	$148.80
Purchase #5	$127.32	7.138%	$136.4081	$136.41	$136.40	$136.40
Purchase #6	$59.86	8.444%	$64.9146	$64.91	$64.90	$64.90
Purchase #7	$200.99	12.218%	$225.547	$225.55	$225.55	$225.50
7 purchase totals =	$869.42		$944.1789	$944.18	$944.15	$944.20