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	$145.46	4.363%	$151.8064	$151.81	$151.80	$151.80
Purchase #2	$28.37	7.367%	$30.46	$30.46	$30.45	$30.50
Purchase #3	$170.29	12.425%	$191.4485	$191.45	$191.45	$191.40
Purchase #4	$248.97	8.270%	$269.5598	$269.56	$269.55	$269.60
Purchase #5	$126.45	11.842%	$141.4242	$141.42	$141.40	$141.40
Purchase #6	$88.86	8.186%	$96.1341	$96.13	$96.15	$96.10
Purchase #7	$89.75	11.412%	$99.9923	$99.99	$100.00	$100.00
7 purchase totals =	$898.15		$980.8253	$980.82	$980.80	$980.80