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	$87.64	5.859%	$92.7748	$92.77	$92.75	$92.80
Purchase #2	$153.94	13.182%	$174.2324	$174.23	$174.25	$174.20
Purchase #3	$98.68	3.256%	$101.893	$101.89	$101.90	$101.90
Purchase #4	$127.34	4.588%	$133.1824	$133.18	$133.20	$133.20
Purchase #5	$37.78	6.439%	$40.2127	$40.21	$40.20	$40.20
Purchase #6	$220.79	10.767%	$244.5625	$244.56	$244.55	$244.60
Purchase #7	$242.89	5.362%	$255.9138	$255.91	$255.90	$255.90
7 purchase totals =	$969.06		$1,042.7716	$1,042.75	$1,042.75	$1,042.80