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	$136.53	4.516%	$142.6957	$142.70	$142.70	$142.70
Purchase #2	$87.86	13.584%	$99.7949	$99.79	$99.80	$99.80
Purchase #3	$61.64	4.449%	$64.3824	$64.38	$64.40	$64.40
Purchase #4	$17.75	9.683%	$19.4687	$19.47	$19.45	$19.50
Purchase #5	$112.69	5.221%	$118.5735	$118.57	$118.55	$118.60
Purchase #6	$75.81	3.300%	$78.3117	$78.31	$78.30	$78.30
Purchase #7	$44.72	12.562%	$50.3377	$50.34	$50.35	$50.30
7 purchase totals =	$537.00		$573.5646	$573.56	$573.55	$573.60