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	$125.55	12.672%	$141.4597	$141.46	$141.45	$141.50
Purchase #2	$237.39	7.517%	$255.2346	$255.23	$255.25	$255.20
Purchase #3	$159.91	9.827%	$175.6244	$175.62	$175.60	$175.60
Purchase #4	$237.36	9.336%	$259.5199	$259.52	$259.50	$259.50
Purchase #5	$94.71	11.199%	$105.3166	$105.32	$105.30	$105.30
Purchase #6	$69.27	3.691%	$71.8268	$71.83	$71.85	$71.80
Purchase #7	$104.78	4.157%	$109.1357	$109.14	$109.15	$109.10
7 purchase totals =	$1,028.97		$1,118.1177	$1,118.12	$1,118.10	$1,118.00