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	$40.93	8.300%	$44.3272	$44.33	$44.35	$44.30
Purchase #2	$105.89	6.731%	$113.0175	$113.02	$113.00	$113.00
Purchase #3	$127.38	11.847%	$142.4707	$142.47	$142.45	$142.50
Purchase #4	$47.42	13.508%	$53.8255	$53.83	$53.85	$53.80
Purchase #5	$78.43	13.174%	$88.7624	$88.76	$88.75	$88.80
Purchase #6	$185.63	9.748%	$203.7252	$203.73	$203.75	$203.70
Purchase #7	$160.82	12.181%	$180.4095	$180.41	$180.40	$180.40
7 purchase totals =	$746.50		$826.5380	$826.55	$826.55	$826.50