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	$120.74	10.103%	$132.9384	$132.94	$132.95	$132.90
Purchase #2	$158.71	13.315%	$179.8422	$179.84	$179.85	$179.80
Purchase #3	$81.82	12.501%	$92.0483	$92.05	$92.05	$92.00
Purchase #4	$104.44	11.123%	$116.0569	$116.06	$116.05	$116.10
Purchase #5	$35.51	13.281%	$40.2261	$40.23	$40.25	$40.20
Purchase #6	$55.59	12.216%	$62.3809	$62.38	$62.40	$62.40
Purchase #7	$6.64	9.505%	$7.2711	$7.27	$7.25	$7.30
7 purchase totals =	$563.45		$630.7639	$630.77	$630.80	$630.70