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	$201.64	3.306%	$208.3062	$208.31	$208.30	$208.30
Purchase #2	$95.96	8.113%	$103.7452	$103.75	$103.75	$103.70
Purchase #3	$48.70	8.744%	$52.9583	$52.96	$52.95	$53.00
Purchase #4	$159.65	8.231%	$172.7908	$172.79	$172.80	$172.80
Purchase #5	$95.48	4.623%	$99.894	$99.89	$99.90	$99.90
Purchase #6	$64.39	11.628%	$71.8773	$71.88	$71.90	$71.90
Purchase #7	$121.82	13.677%	$138.4813	$138.48	$138.50	$138.50
7 purchase totals =	$787.64		$848.0531	$848.06	$848.10	$848.10