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	$39.40	10.799%	$43.6548	$43.65	$43.65	$43.70
Purchase #2	$88.35	3.115%	$91.1021	$91.10	$91.10	$91.10
Purchase #3	$145.63	13.159%	$164.7935	$164.79	$164.80	$164.80
Purchase #4	$161.27	3.637%	$167.1354	$167.14	$167.15	$167.10
Purchase #5	$122.52	13.768%	$139.3886	$139.39	$139.40	$139.40
Purchase #6	$104.32	4.114%	$108.6117	$108.61	$108.60	$108.60
Purchase #7	$69.90	3.668%	$72.4639	$72.46	$72.45	$72.50
7 purchase totals =	$731.39		$787.1500	$787.14	$787.15	$787.20