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	$64.72	12.782%	$72.9925	$72.99	$73.00	$73.00
Purchase #2	$21.72	3.740%	$22.5323	$22.53	$22.55	$22.50
Purchase #3	$67.53	7.462%	$72.5691	$72.57	$72.55	$72.60
Purchase #4	$82.72	12.806%	$93.3131	$93.31	$93.30	$93.30
Purchase #5	$141.52	4.182%	$147.4384	$147.44	$147.45	$147.40
Purchase #6	$123.70	6.362%	$131.5698	$131.57	$131.55	$131.60
Purchase #7	$236.30	3.530%	$244.6414	$244.64	$244.65	$244.60
7 purchase totals =	$738.21		$785.0566	$785.05	$785.05	$785.00