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	$57.34	7.212%	$61.4754	$61.48	$61.50	$61.50
Purchase #2	$123.30	6.873%	$131.7744	$131.77	$131.75	$131.80
Purchase #3	$138.78	11.625%	$154.9132	$154.91	$154.90	$154.90
Purchase #4	$78.63	12.153%	$88.1859	$88.19	$88.20	$88.20
Purchase #5	$151.81	8.239%	$164.3176	$164.32	$164.30	$164.30
Purchase #6	$176.59	10.708%	$195.4993	$195.50	$195.50	$195.50
Purchase #7	$28.89	4.874%	$30.2981	$30.30	$30.30	$30.30
7 purchase totals =	$755.34		$826.4639	$826.47	$826.45	$826.50