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	$93.90	7.252%	$100.7096	$100.71	$100.70	$100.70
Purchase #2	$235.50	4.566%	$246.2529	$246.25	$246.25	$246.30
Purchase #3	$96.28	9.367%	$105.2985	$105.30	$105.30	$105.30
Purchase #4	$238.94	10.499%	$264.0263	$264.03	$264.05	$264.00
Purchase #5	$151.41	7.330%	$162.5084	$162.51	$162.50	$162.50
Purchase #6	$178.30	12.110%	$199.8921	$199.89	$199.90	$199.90
Purchase #7	$145.47	6.846%	$155.4289	$155.43	$155.45	$155.40
7 purchase totals =	$1,139.80		$1,234.1167	$1,234.12	$1,234.15	$1,234.10