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	$127.95	10.615%	$141.5319	$141.53	$141.55	$141.50
Purchase #2	$132.75	3.235%	$137.0445	$137.04	$137.05	$137.00
Purchase #3	$75.59	9.502%	$82.7726	$82.77	$82.75	$82.80
Purchase #4	$162.86	11.796%	$182.071	$182.07	$182.05	$182.10
Purchase #5	$194.40	12.355%	$218.4181	$218.42	$218.40	$218.40
Purchase #6	$139.72	5.140%	$146.9016	$146.90	$146.90	$146.90
Purchase #7	$92.26	12.824%	$104.0914	$104.09	$104.10	$104.10
7 purchase totals =	$925.53		$1,012.8311	$1,012.82	$1,012.80	$1,012.80