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	$154.48	7.316%	$165.7818	$165.78	$165.80	$165.80
Purchase #2	$151.85	11.115%	$168.7281	$168.73	$168.75	$168.70
Purchase #3	$148.29	7.584%	$159.5363	$159.54	$159.55	$159.50
Purchase #4	$201.56	11.557%	$224.8543	$224.85	$224.85	$224.90
Purchase #5	$83.38	7.566%	$89.6885	$89.69	$89.70	$89.70
Purchase #6	$162.48	9.314%	$177.6134	$177.61	$177.60	$177.60
Purchase #7	$30.31	8.792%	$32.9749	$32.97	$32.95	$33.00
7 purchase totals =	$932.35		$1,019.1773	$1,019.17	$1,019.20	$1,019.20