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	$147.77	11.301%	$164.4695	$164.47	$164.45	$164.50
Purchase #2	$172.91	4.275%	$180.3019	$180.30	$180.30	$180.30
Purchase #3	$104.75	10.798%	$116.0609	$116.06	$116.05	$116.10
Purchase #4	$56.46	10.658%	$62.4775	$62.48	$62.50	$62.50
Purchase #5	$28.42	13.158%	$32.1595	$32.16	$32.15	$32.20
Purchase #6	$44.61	6.613%	$47.5601	$47.56	$47.55	$47.60
Purchase #7	$181.82	10.312%	$200.5693	$200.57	$200.55	$200.60
7 purchase totals =	$736.74		$803.5987	$803.60	$803.55	$803.80