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	$76.83	7.733%	$82.7713	$82.77	$82.75	$82.80
Purchase #2	$222.33	6.442%	$236.6525	$236.65	$236.65	$236.70
Purchase #3	$127.62	12.589%	$143.6861	$143.69	$143.70	$143.70
Purchase #4	$222.98	8.570%	$242.0894	$242.09	$242.10	$242.10
Purchase #5	$51.61	3.281%	$53.3033	$53.30	$53.30	$53.30
Purchase #6	$96.39	5.535%	$101.7252	$101.73	$101.75	$101.70
Purchase #7	$70.62	10.558%	$78.0761	$78.08	$78.10	$78.10
7 purchase totals =	$868.38		$938.3039	$938.31	$938.35	$938.40