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	$198.68	9.554%	$217.6619	$217.66	$217.65	$217.70
Purchase #2	$84.69	11.748%	$94.6394	$94.64	$94.65	$94.60
Purchase #3	$188.45	3.132%	$194.3523	$194.35	$194.35	$194.40
Purchase #4	$68.85	5.188%	$72.4219	$72.42	$72.40	$72.40
Purchase #5	$92.80	9.591%	$101.7004	$101.70	$101.70	$101.70
Purchase #6	$50.31	4.698%	$52.6736	$52.67	$52.65	$52.70
Purchase #7	$52.34	13.609%	$59.463	$59.46	$59.45	$59.50
7 purchase totals =	$736.12		$792.9125	$792.90	$792.85	$793.00