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	$224.55	13.666%	$255.237	$255.24	$255.25	$255.20
Purchase #2	$116.25	11.317%	$129.406	$129.41	$129.40	$129.40
Purchase #3	$249.79	8.350%	$270.6475	$270.65	$270.65	$270.60
Purchase #4	$65.48	7.266%	$70.2378	$70.24	$70.25	$70.20
Purchase #5	$206.61	7.671%	$222.4591	$222.46	$222.45	$222.50
Purchase #6	$109.45	4.651%	$114.5405	$114.54	$114.55	$114.50
Purchase #7	$96.51	9.596%	$105.7711	$105.77	$105.75	$105.80
7 purchase totals =	$1,068.64		$1,168.2990	$1,168.31	$1,168.30	$1,168.20