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	$229.44	10.561%	$253.6712	$253.67	$253.65	$253.70
Purchase #2	$43.85	10.389%	$48.4056	$48.41	$48.40	$48.40
Purchase #3	$226.31	9.607%	$248.0516	$248.05	$248.05	$248.10
Purchase #4	$51.89	7.705%	$55.8881	$55.89	$55.90	$55.90
Purchase #5	$39.78	5.298%	$41.8875	$41.89	$41.90	$41.90
Purchase #6	$18.61	4.480%	$19.4437	$19.44	$19.45	$19.40
Purchase #7	$150.76	5.179%	$158.5679	$158.57	$158.55	$158.60
7 purchase totals =	$760.64		$825.9156	$825.92	$825.90	$826.00