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	$216.91	7.508%	$233.1956	$233.20	$233.20	$233.20
Purchase #2	$80.28	11.555%	$89.5564	$89.56	$89.55	$89.60
Purchase #3	$80.93	11.320%	$90.0913	$90.09	$90.10	$90.10
Purchase #4	$229.44	5.649%	$242.4011	$242.40	$242.40	$242.40
Purchase #5	$70.50	10.433%	$77.8553	$77.86	$77.85	$77.90
Purchase #6	$67.85	6.778%	$72.4489	$72.45	$72.45	$72.40
Purchase #7	$43.31	6.322%	$46.0481	$46.05	$46.05	$46.00
7 purchase totals =	$789.22		$851.5967	$851.61	$851.60	$851.60