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	$173.86	10.210%	$191.6111	$191.61	$191.60	$191.60
Purchase #2	$10.67	5.302%	$11.2357	$11.24	$11.25	$11.20
Purchase #3	$230.30	3.616%	$238.6276	$238.63	$238.65	$238.60
Purchase #4	$184.25	5.636%	$194.6343	$194.63	$194.65	$194.60
Purchase #5	$193.77	3.281%	$200.1276	$200.13	$200.15	$200.10
Purchase #6	$46.37	11.839%	$51.8597	$51.86	$51.85	$51.90
Purchase #7	$206.51	5.402%	$217.6657	$217.67	$217.65	$217.70
7 purchase totals =	$1,045.73		$1,105.7617	$1,105.77	$1,105.80	$1,105.70