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	$31.30	3.284%	$32.3279	$32.33	$32.35	$32.30
Purchase #2	$17.46	3.507%	$18.0723	$18.07	$18.05	$18.10
Purchase #3	$73.45	10.436%	$81.1152	$81.12	$81.10	$81.10
Purchase #4	$89.88	6.156%	$95.413	$95.41	$95.40	$95.40
Purchase #5	$38.26	3.125%	$39.4556	$39.46	$39.45	$39.50
Purchase #6	$91.70	12.328%	$103.0048	$103.00	$103.00	$103.00
Purchase #7	$123.75	10.318%	$136.5185	$136.52	$136.50	$136.50
7 purchase totals =	$465.80		$505.9073	$505.91	$505.85	$505.90