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	$129.34	12.524%	$145.5385	$145.54	$145.55	$145.50
Purchase #2	$103.56	7.223%	$111.0401	$111.04	$111.05	$111.00
Purchase #3	$247.38	11.223%	$275.1435	$275.14	$275.15	$275.10
Purchase #4	$139.90	8.824%	$152.2448	$152.24	$152.25	$152.20
Purchase #5	$184.57	13.772%	$209.989	$209.99	$210.00	$210.00
Purchase #6	$116.77	6.649%	$124.534	$124.53	$124.55	$124.50
Purchase #7	$217.31	13.849%	$247.4053	$247.41	$247.40	$247.40
7 purchase totals =	$1,138.83		$1,265.8952	$1,265.89	$1,265.95	$1,265.70