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	$140.40	7.632%	$151.1153	$151.12	$151.10	$151.10
Purchase #2	$95.66	13.287%	$108.3703	$108.37	$108.35	$108.40
Purchase #3	$224.51	4.573%	$234.7768	$234.78	$234.80	$234.80
Purchase #4	$79.81	13.787%	$90.8134	$90.81	$90.80	$90.80
Purchase #5	$165.28	9.644%	$181.2196	$181.22	$181.20	$181.20
Purchase #6	$47.34	7.194%	$50.7456	$50.75	$50.75	$50.70
Purchase #7	$109.39	13.174%	$123.801	$123.80	$123.80	$123.80
7 purchase totals =	$862.39		$940.8420	$940.85	$940.80	$940.80