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	$188.86	3.328%	$195.1453	$195.15	$195.15	$195.10
Purchase #2	$136.71	8.344%	$148.1171	$148.12	$148.10	$148.10
Purchase #3	$109.55	10.564%	$121.1229	$121.12	$121.10	$121.10
Purchase #4	$47.83	5.690%	$50.5515	$50.55	$50.55	$50.60
Purchase #5	$229.47	4.834%	$240.5626	$240.56	$240.55	$240.60
Purchase #6	$112.78	10.710%	$124.8587	$124.86	$124.85	$124.90
Purchase #7	$43.52	5.315%	$45.8331	$45.83	$45.85	$45.80
7 purchase totals =	$868.72		$926.1912	$926.19	$926.15	$926.20