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	$58.51	12.214%	$65.6564	$65.66	$65.65	$65.70
Purchase #2	$136.31	11.426%	$151.8848	$151.88	$151.90	$151.90
Purchase #3	$56.62	11.303%	$63.0198	$63.02	$63.00	$63.00
Purchase #4	$41.73	6.794%	$44.5651	$44.57	$44.55	$44.60
Purchase #5	$42.91	3.456%	$44.393	$44.39	$44.40	$44.40
Purchase #6	$210.46	9.105%	$229.6224	$229.62	$229.60	$229.60
Purchase #7	$179.80	11.326%	$200.1641	$200.16	$200.15	$200.20
7 purchase totals =	$726.34		$799.3056	$799.30	$799.25	$799.40