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	$40.61	11.142%	$45.1348	$45.13	$45.15	$45.10
Purchase #2	$110.70	11.489%	$123.4183	$123.42	$123.40	$123.40
Purchase #3	$216.64	11.129%	$240.7499	$240.75	$240.75	$240.70
Purchase #4	$152.47	12.679%	$171.8017	$171.80	$171.80	$171.80
Purchase #5	$47.36	11.174%	$52.652	$52.65	$52.65	$52.70
Purchase #6	$145.43	7.859%	$156.8593	$156.86	$156.85	$156.90
Purchase #7	$83.48	9.255%	$91.2061	$91.21	$91.20	$91.20
7 purchase totals =	$796.69		$881.8221	$881.82	$881.80	$881.80