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	$247.69	3.272%	$255.7944	$255.79	$255.80	$255.80
Purchase #2	$93.55	11.345%	$104.1632	$104.16	$104.15	$104.20
Purchase #3	$184.99	13.615%	$210.1764	$210.18	$210.20	$210.20
Purchase #4	$81.73	4.556%	$85.4536	$85.45	$85.45	$85.50
Purchase #5	$123.55	3.771%	$128.2091	$128.21	$128.20	$128.20
Purchase #6	$206.69	4.778%	$216.5656	$216.57	$216.55	$216.60
Purchase #7	$240.63	6.106%	$255.3229	$255.32	$255.30	$255.30
7 purchase totals =	$1,178.83		$1,255.6852	$1,255.68	$1,255.65	$1,255.80