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	$191.84	7.523%	$206.2721	$206.27	$206.25	$206.30
Purchase #2	$124.95	11.566%	$139.4017	$139.40	$139.40	$139.40
Purchase #3	$126.27	3.478%	$130.6617	$130.66	$130.65	$130.70
Purchase #4	$158.82	10.630%	$175.7026	$175.70	$175.70	$175.70
Purchase #5	$51.47	4.121%	$53.5911	$53.59	$53.60	$53.60
Purchase #6	$80.76	10.723%	$89.4199	$89.42	$89.40	$89.40
Purchase #7	$230.25	6.531%	$245.2876	$245.29	$245.30	$245.30
7 purchase totals =	$964.36		$1,040.3367	$1,040.33	$1,040.30	$1,040.40