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	$114.95	3.302%	$118.7456	$118.75	$118.75	$118.70
Purchase #2	$128.37	10.360%	$141.6691	$141.67	$141.65	$141.70
Purchase #3	$175.76	6.150%	$186.5692	$186.57	$186.55	$186.60
Purchase #4	$20.94	9.625%	$22.9555	$22.96	$22.95	$23.00
Purchase #5	$89.43	10.843%	$99.1269	$99.13	$99.15	$99.10
Purchase #6	$40.80	11.871%	$45.6434	$45.64	$45.65	$45.60
Purchase #7	$215.34	3.321%	$222.4914	$222.49	$222.50	$222.50
7 purchase totals =	$785.59		$837.2011	$837.21	$837.20	$837.20