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	$96.35	10.649%	$106.6103	$106.61	$106.60	$106.60
Purchase #2	$82.97	4.434%	$86.6489	$86.65	$86.65	$86.60
Purchase #3	$59.50	3.372%	$61.5063	$61.51	$61.50	$61.50
Purchase #4	$227.40	9.426%	$248.8347	$248.83	$248.85	$248.80
Purchase #5	$141.76	12.803%	$159.9095	$159.91	$159.90	$159.90
Purchase #6	$245.34	7.424%	$263.554	$263.55	$263.55	$263.60
Purchase #7	$154.50	9.138%	$168.6182	$168.62	$168.60	$168.60
7 purchase totals =	$1,007.82		$1,095.6819	$1,095.68	$1,095.65	$1,095.60