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	$62.55	5.453%	$65.9609	$65.96	$65.95	$66.00
Purchase #2	$148.29	11.383%	$165.1699	$165.17	$165.15	$165.20
Purchase #3	$219.35	4.752%	$229.7735	$229.77	$229.75	$229.80
Purchase #4	$168.89	10.848%	$187.2112	$187.21	$187.20	$187.20
Purchase #5	$144.68	5.344%	$152.4117	$152.41	$152.40	$152.40
Purchase #6	$137.93	13.308%	$156.2857	$156.29	$156.30	$156.30
Purchase #7	$233.51	4.260%	$243.4575	$243.46	$243.45	$243.50
7 purchase totals =	$1,115.20		$1,200.2704	$1,200.27	$1,200.20	$1,200.40