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	$77.56	9.730%	$85.1066	$85.11	$85.10	$85.10
Purchase #2	$234.54	3.346%	$242.3877	$242.39	$242.40	$242.40
Purchase #3	$48.26	13.746%	$54.8938	$54.89	$54.90	$54.90
Purchase #4	$49.52	5.360%	$52.1743	$52.17	$52.15	$52.20
Purchase #5	$196.68	3.654%	$203.8667	$203.87	$203.85	$203.90
Purchase #6	$136.76	13.403%	$155.0899	$155.09	$155.10	$155.10
Purchase #7	$38.80	7.225%	$41.6033	$41.60	$41.60	$41.60
7 purchase totals =	$782.12		$835.1223	$835.12	$835.10	$835.20