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	$194.85	8.353%	$211.1258	$211.13	$211.15	$211.10
Purchase #2	$45.28	6.153%	$48.0661	$48.07	$48.05	$48.10
Purchase #3	$149.80	8.511%	$162.5495	$162.55	$162.55	$162.50
Purchase #4	$95.42	3.255%	$98.5259	$98.53	$98.55	$98.50
Purchase #5	$196.91	12.647%	$221.8132	$221.81	$221.80	$221.80
Purchase #6	$128.31	11.793%	$143.4416	$143.44	$143.45	$143.40
Purchase #7	$103.51	7.647%	$111.4254	$111.43	$111.45	$111.40
7 purchase totals =	$914.08		$996.9475	$996.96	$997.00	$996.80