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	$67.53	5.429%	$71.1962	$71.20	$71.20	$71.20
Purchase #2	$141.76	8.284%	$153.5034	$153.50	$153.50	$153.50
Purchase #3	$225.81	3.812%	$234.4179	$234.42	$234.40	$234.40
Purchase #4	$40.90	4.254%	$42.6399	$42.64	$42.65	$42.60
Purchase #5	$110.85	6.309%	$117.8435	$117.84	$117.85	$117.80
Purchase #6	$220.74	12.180%	$247.6261	$247.63	$247.65	$247.60
Purchase #7	$136.66	11.793%	$152.7763	$152.78	$152.80	$152.80
7 purchase totals =	$944.25		$1,020.0033	$1,020.01	$1,020.05	$1,019.90