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	$202.63	10.301%	$223.5029	$223.50	$223.50	$223.50
Purchase #2	$37.65	11.508%	$41.9828	$41.98	$42.00	$42.00
Purchase #3	$84.66	11.433%	$94.3392	$94.34	$94.35	$94.30
Purchase #4	$97.26	12.427%	$109.3465	$109.35	$109.35	$109.30
Purchase #5	$62.59	12.502%	$70.415	$70.42	$70.40	$70.40
Purchase #6	$231.42	10.123%	$254.8466	$254.85	$254.85	$254.80
Purchase #7	$200.66	10.621%	$221.9721	$221.97	$221.95	$222.00
7 purchase totals =	$916.87		$1,016.4051	$1,016.41	$1,016.40	$1,016.30