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	$108.33	3.547%	$112.1725	$112.17	$112.15	$112.20
Purchase #2	$70.59	3.828%	$73.2922	$73.29	$73.30	$73.30
Purchase #3	$219.48	9.284%	$239.8565	$239.86	$239.85	$239.90
Purchase #4	$10.79	13.820%	$12.2812	$12.28	$12.30	$12.30
Purchase #5	$79.37	3.748%	$82.3448	$82.34	$82.35	$82.30
Purchase #6	$133.34	5.408%	$140.551	$140.55	$140.55	$140.60
Purchase #7	$130.61	12.462%	$146.8866	$146.89	$146.90	$146.90
7 purchase totals =	$752.51		$807.3848	$807.38	$807.40	$807.50