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	$227.67	8.740%	$247.5684	$247.57	$247.55	$247.60
Purchase #2	$90.56	9.569%	$99.2257	$99.23	$99.25	$99.20
Purchase #3	$202.61	10.706%	$224.3014	$224.30	$224.30	$224.30
Purchase #4	$69.49	4.818%	$72.838	$72.84	$72.85	$72.80
Purchase #5	$202.77	6.637%	$216.2278	$216.23	$216.25	$216.20
Purchase #6	$85.29	10.630%	$94.3563	$94.36	$94.35	$94.40
Purchase #7	$59.37	4.104%	$61.8065	$61.81	$61.80	$61.80
7 purchase totals =	$937.76		$1,016.3241	$1,016.34	$1,016.35	$1,016.30