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	$128.56	10.682%	$142.2928	$142.29	$142.30	$142.30
Purchase #2	$158.60	11.804%	$177.3211	$177.32	$177.30	$177.30
Purchase #3	$159.31	3.433%	$164.7791	$164.78	$164.80	$164.80
Purchase #4	$12.95	10.221%	$14.2736	$14.27	$14.25	$14.30
Purchase #5	$38.88	9.107%	$42.4208	$42.42	$42.40	$42.40
Purchase #6	$23.48	13.281%	$26.5984	$26.60	$26.60	$26.60
Purchase #7	$136.57	7.364%	$146.627	$146.63	$146.65	$146.60
7 purchase totals =	$658.35		$714.3128	$714.31	$714.30	$714.30