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	$170.62	10.125%	$187.8953	$187.90	$187.90	$187.90
Purchase #2	$73.52	7.268%	$78.8634	$78.86	$78.85	$78.90
Purchase #3	$164.51	3.269%	$169.8878	$169.89	$169.90	$169.90
Purchase #4	$83.82	8.211%	$90.7025	$90.70	$90.70	$90.70
Purchase #5	$26.30	4.110%	$27.3809	$27.38	$27.40	$27.40
Purchase #6	$132.73	11.184%	$147.5745	$147.57	$147.55	$147.60
Purchase #7	$110.71	12.679%	$124.7469	$124.75	$124.75	$124.70
7 purchase totals =	$762.21		$827.0513	$827.05	$827.05	$827.10