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	$177.25	12.196%	$198.8674	$198.87	$198.85	$198.90
Purchase #2	$42.81	11.130%	$47.5748	$47.57	$47.55	$47.60
Purchase #3	$243.44	5.790%	$257.5352	$257.54	$257.55	$257.50
Purchase #4	$62.57	11.758%	$69.927	$69.93	$69.95	$69.90
Purchase #5	$104.38	11.412%	$116.2918	$116.29	$116.30	$116.30
Purchase #6	$135.65	5.701%	$143.3834	$143.38	$143.40	$143.40
Purchase #7	$152.76	11.225%	$169.9073	$169.91	$169.90	$169.90
7 purchase totals =	$918.86		$1,003.4869	$1,003.49	$1,003.50	$1,003.50