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	$198.74	3.703%	$206.0993	$206.10	$206.10	$206.10
Purchase #2	$217.77	3.637%	$225.6903	$225.69	$225.70	$225.70
Purchase #3	$130.45	11.330%	$145.23	$145.23	$145.25	$145.20
Purchase #4	$28.89	8.868%	$31.452	$31.45	$31.45	$31.50
Purchase #5	$105.80	13.715%	$120.3105	$120.31	$120.30	$120.30
Purchase #6	$83.57	8.747%	$90.8799	$90.88	$90.90	$90.90
Purchase #7	$78.92	6.119%	$83.7491	$83.75	$83.75	$83.70
7 purchase totals =	$844.14		$903.4111	$903.41	$903.45	$903.40