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	$41.38	3.387%	$42.7815	$42.78	$42.80	$42.80
Purchase #2	$91.83	3.450%	$94.9981	$95.00	$95.00	$95.00
Purchase #3	$218.76	11.598%	$244.1318	$244.13	$244.15	$244.10
Purchase #4	$176.56	8.192%	$191.0238	$191.02	$191.00	$191.00
Purchase #5	$118.41	12.171%	$132.8217	$132.82	$132.80	$132.80
Purchase #6	$54.90	12.558%	$61.7943	$61.79	$61.80	$61.80
Purchase #7	$116.56	12.132%	$130.7011	$130.70	$130.70	$130.70
7 purchase totals =	$818.40		$898.2523	$898.24	$898.25	$898.20