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	$200.74	12.130%	$225.0898	$225.09	$225.10	$225.10
Purchase #2	$131.61	8.671%	$143.0219	$143.02	$143.00	$143.00
Purchase #3	$114.72	7.862%	$123.7393	$123.74	$123.75	$123.70
Purchase #4	$207.33	5.410%	$218.5466	$218.55	$218.55	$218.50
Purchase #5	$144.40	5.356%	$152.1341	$152.13	$152.15	$152.10
Purchase #6	$246.99	8.286%	$267.4556	$267.46	$267.45	$267.50
Purchase #7	$158.38	4.113%	$164.8942	$164.89	$164.90	$164.90
7 purchase totals =	$1,204.17		$1,294.8815	$1,294.88	$1,294.90	$1,294.80