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	$246.76	11.574%	$275.32	$275.32	$275.30	$275.30
Purchase #2	$19.29	5.776%	$20.4042	$20.40	$20.40	$20.40
Purchase #3	$101.32	4.567%	$105.9473	$105.95	$105.95	$105.90
Purchase #4	$38.57	11.798%	$43.1205	$43.12	$43.10	$43.10
Purchase #5	$221.99	10.200%	$244.633	$244.63	$244.65	$244.60
Purchase #6	$71.34	9.399%	$78.0452	$78.05	$78.05	$78.00
Purchase #7	$95.76	3.232%	$98.855	$98.86	$98.85	$98.90
7 purchase totals =	$795.03		$866.3252	$866.33	$866.30	$866.20