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	$190.91	10.303%	$210.5795	$210.58	$210.60	$210.60
Purchase #2	$142.38	10.400%	$157.1875	$157.19	$157.20	$157.20
Purchase #3	$237.54	13.727%	$270.1471	$270.15	$270.15	$270.10
Purchase #4	$139.47	3.708%	$144.6415	$144.64	$144.65	$144.60
Purchase #5	$136.51	11.151%	$151.7322	$151.73	$151.75	$151.70
Purchase #6	$120.96	13.752%	$137.5944	$137.59	$137.60	$137.60
Purchase #7	$140.58	6.870%	$150.2378	$150.24	$150.25	$150.20
7 purchase totals =	$1,108.35		$1,222.1200	$1,222.12	$1,222.20	$1,222.00