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	$56.28	4.311%	$58.7062	$58.71	$58.70	$58.70
Purchase #2	$152.76	12.541%	$171.9176	$171.92	$171.90	$171.90
Purchase #3	$179.65	11.230%	$199.8247	$199.82	$199.80	$199.80
Purchase #4	$65.36	3.824%	$67.8594	$67.86	$67.85	$67.90
Purchase #5	$10.51	10.124%	$11.574	$11.57	$11.55	$11.60
Purchase #6	$198.31	11.276%	$220.6714	$220.67	$220.65	$220.70
Purchase #7	$58.94	11.796%	$65.8926	$65.89	$65.90	$65.90
7 purchase totals =	$721.81		$796.4459	$796.44	$796.35	$796.50