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	$231.33	13.381%	$262.2843	$262.28	$262.30	$262.30
Purchase #2	$177.99	10.385%	$196.4743	$196.47	$196.45	$196.50
Purchase #3	$48.48	10.219%	$53.4342	$53.43	$53.45	$53.40
Purchase #4	$132.71	7.506%	$142.6712	$142.67	$142.65	$142.70
Purchase #5	$207.27	7.266%	$222.3302	$222.33	$222.35	$222.30
Purchase #6	$190.73	4.418%	$199.1565	$199.16	$199.15	$199.20
Purchase #7	$85.76	8.845%	$93.3455	$93.35	$93.35	$93.30
7 purchase totals =	$1,074.27		$1,169.6962	$1,169.69	$1,169.70	$1,169.70