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	$91.53	11.711%	$102.2491	$102.25	$102.25	$102.20
Purchase #2	$51.53	5.237%	$54.2286	$54.23	$54.25	$54.20
Purchase #3	$62.50	13.759%	$71.0994	$71.10	$71.10	$71.10
Purchase #4	$104.78	11.182%	$116.4965	$116.50	$116.50	$116.50
Purchase #5	$20.34	9.280%	$22.2276	$22.23	$22.25	$22.20
Purchase #6	$58.82	3.793%	$61.051	$61.05	$61.05	$61.10
Purchase #7	$188.45	5.646%	$199.0899	$199.09	$199.10	$199.10
7 purchase totals =	$577.95		$626.4421	$626.45	$626.50	$626.40