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	$133.89	7.376%	$143.7657	$143.77	$143.75	$143.80
Purchase #2	$185.26	13.428%	$210.1367	$210.14	$210.15	$210.10
Purchase #3	$72.73	11.804%	$81.315	$81.32	$81.30	$81.30
Purchase #4	$72.73	8.141%	$78.6509	$78.65	$78.65	$78.70
Purchase #5	$81.64	10.102%	$89.8873	$89.89	$89.90	$89.90
Purchase #6	$52.54	11.462%	$58.5621	$58.56	$58.55	$58.60
Purchase #7	$195.59	4.290%	$203.9808	$203.98	$204.00	$204.00
7 purchase totals =	$794.38		$866.2985	$866.31	$866.30	$866.40