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	$187.34	10.244%	$206.5311	$206.53	$206.55	$206.50
Purchase #2	$67.93	6.598%	$72.412	$72.41	$72.40	$72.40
Purchase #3	$153.53	12.328%	$172.4572	$172.46	$172.45	$172.50
Purchase #4	$130.89	10.342%	$144.4266	$144.43	$144.45	$144.40
Purchase #5	$154.78	7.218%	$165.952	$165.95	$165.95	$166.00
Purchase #6	$147.48	13.497%	$167.3854	$167.39	$167.40	$167.40
Purchase #7	$203.33	7.699%	$218.9844	$218.98	$219.00	$219.00
7 purchase totals =	$1,045.28		$1,148.1487	$1,148.15	$1,148.20	$1,148.20