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	$50.29	7.728%	$54.1764	$54.18	$54.20	$54.20
Purchase #2	$165.86	3.802%	$172.166	$172.17	$172.15	$172.20
Purchase #3	$240.95	6.192%	$255.8696	$255.87	$255.85	$255.90
Purchase #4	$188.31	4.788%	$197.3263	$197.33	$197.35	$197.30
Purchase #5	$170.25	5.306%	$179.2835	$179.28	$179.30	$179.30
Purchase #6	$26.75	3.557%	$27.7015	$27.70	$27.70	$27.70
Purchase #7	$238.41	7.192%	$255.5564	$255.56	$255.55	$255.60
7 purchase totals =	$1,080.82		$1,142.0797	$1,142.09	$1,142.10	$1,142.20