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	$248.86	6.363%	$264.695	$264.70	$264.70	$264.70
Purchase #2	$51.89	6.440%	$55.2317	$55.23	$55.25	$55.20
Purchase #3	$74.29	5.191%	$78.1464	$78.15	$78.15	$78.10
Purchase #4	$191.86	11.444%	$213.8165	$213.82	$213.80	$213.80
Purchase #5	$138.62	8.866%	$150.91	$150.91	$150.90	$150.90
Purchase #6	$127.82	3.573%	$132.387	$132.39	$132.40	$132.40
Purchase #7	$145.67	8.762%	$158.4336	$158.43	$158.45	$158.40
7 purchase totals =	$979.01		$1,053.6202	$1,053.63	$1,053.65	$1,053.50