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	$101.86	9.807%	$111.8494	$111.85	$111.85	$111.80
Purchase #2	$152.94	3.419%	$158.169	$158.17	$158.15	$158.20
Purchase #3	$35.91	6.214%	$38.1414	$38.14	$38.15	$38.10
Purchase #4	$206.53	6.571%	$220.1011	$220.10	$220.10	$220.10
Purchase #5	$50.73	6.363%	$53.9579	$53.96	$53.95	$54.00
Purchase #6	$80.87	3.709%	$83.8695	$83.87	$83.85	$83.90
Purchase #7	$58.30	12.385%	$65.5205	$65.52	$65.50	$65.50
7 purchase totals =	$687.14		$731.6088	$731.61	$731.55	$731.60