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	$42.43	6.869%	$45.3445	$45.34	$45.35	$45.30
Purchase #2	$21.82	3.219%	$22.5224	$22.52	$22.50	$22.50
Purchase #3	$72.45	3.650%	$75.0944	$75.09	$75.10	$75.10
Purchase #4	$94.74	12.759%	$106.8279	$106.83	$106.85	$106.80
Purchase #5	$191.31	9.446%	$209.3811	$209.38	$209.40	$209.40
Purchase #6	$5.46	7.825%	$5.8872	$5.89	$5.90	$5.90
Purchase #7	$213.82	9.210%	$233.5128	$233.51	$233.50	$233.50
7 purchase totals =	$642.03		$698.5703	$698.56	$698.60	$698.50