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	$102.39	11.823%	$114.4956	$114.50	$114.50	$114.50
Purchase #2	$124.45	3.746%	$129.1119	$129.11	$129.10	$129.10
Purchase #3	$83.25	7.452%	$89.4538	$89.45	$89.45	$89.50
Purchase #4	$140.43	7.650%	$151.1729	$151.17	$151.15	$151.20
Purchase #5	$238.70	12.532%	$268.6139	$268.61	$268.60	$268.60
Purchase #6	$65.35	11.352%	$72.7685	$72.77	$72.75	$72.80
Purchase #7	$181.77	9.637%	$199.2872	$199.29	$199.30	$199.30
7 purchase totals =	$936.34		$1,024.9038	$1,024.90	$1,024.85	$1,025.00