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	$210.67	5.406%	$222.0588	$222.06	$222.05	$222.10
Purchase #2	$43.31	3.648%	$44.8899	$44.89	$44.90	$44.90
Purchase #3	$122.76	11.507%	$136.886	$136.89	$136.90	$136.90
Purchase #4	$91.33	6.334%	$97.1148	$97.11	$97.10	$97.10
Purchase #5	$119.48	11.625%	$133.3696	$133.37	$133.35	$133.40
Purchase #6	$142.82	6.407%	$151.9705	$151.97	$151.95	$152.00
Purchase #7	$83.42	8.219%	$90.2763	$90.28	$90.30	$90.30
7 purchase totals =	$813.79		$876.5659	$876.57	$876.55	$876.70