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	$173.98	7.331%	$186.7345	$186.73	$186.75	$186.70
Purchase #2	$148.67	5.687%	$157.1249	$157.12	$157.10	$157.10
Purchase #3	$211.70	5.404%	$223.1403	$223.14	$223.15	$223.10
Purchase #4	$88.38	13.639%	$100.4341	$100.43	$100.45	$100.40
Purchase #5	$242.45	3.674%	$251.3576	$251.36	$251.35	$251.40
Purchase #6	$6.88	9.561%	$7.5378	$7.54	$7.55	$7.50
Purchase #7	$77.53	11.568%	$86.4987	$86.50	$86.50	$86.50
7 purchase totals =	$949.59		$1,012.8279	$1,012.82	$1,012.85	$1,012.70