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	$232.38	13.780%	$264.402	$264.40	$264.40	$264.40
Purchase #2	$128.43	10.320%	$141.684	$141.68	$141.70	$141.70
Purchase #3	$207.94	7.464%	$223.4606	$223.46	$223.45	$223.50
Purchase #4	$153.72	5.588%	$162.3099	$162.31	$162.30	$162.30
Purchase #5	$173.33	5.806%	$183.3935	$183.39	$183.40	$183.40
Purchase #6	$233.60	13.821%	$265.8859	$265.89	$265.90	$265.90
Purchase #7	$238.98	4.822%	$250.5036	$250.50	$250.50	$250.50
7 purchase totals =	$1,368.38		$1,491.6395	$1,491.63	$1,491.65	$1,491.70