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	$41.89	13.849%	$47.6913	$47.69	$47.70	$47.70
Purchase #2	$72.59	6.415%	$77.2466	$77.25	$77.25	$77.20
Purchase #3	$165.55	6.478%	$176.2743	$176.27	$176.25	$176.30
Purchase #4	$42.33	12.741%	$47.7233	$47.72	$47.70	$47.70
Purchase #5	$136.88	13.464%	$155.3095	$155.31	$155.30	$155.30
Purchase #6	$151.87	11.280%	$169.0009	$169.00	$169.00	$169.00
Purchase #7	$83.50	5.662%	$88.2278	$88.23	$88.25	$88.20
7 purchase totals =	$694.61		$761.4737	$761.47	$761.45	$761.40