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	$243.78	5.293%	$256.6833	$256.68	$256.70	$256.70
Purchase #2	$107.85	4.301%	$112.4886	$112.49	$112.50	$112.50
Purchase #3	$215.52	4.148%	$224.4598	$224.46	$224.45	$224.50
Purchase #4	$176.42	11.520%	$196.7436	$196.74	$196.75	$196.70
Purchase #5	$242.67	10.399%	$267.9053	$267.91	$267.90	$267.90
Purchase #6	$84.40	3.194%	$87.0957	$87.10	$87.10	$87.10
Purchase #7	$25.75	10.547%	$28.4659	$28.47	$28.45	$28.50
7 purchase totals =	$1,096.39		$1,173.8422	$1,173.85	$1,173.85	$1,173.90