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	$207.27	5.392%	$218.446	$218.45	$218.45	$218.40
Purchase #2	$211.70	3.860%	$219.8716	$219.87	$219.85	$219.90
Purchase #3	$135.63	4.379%	$141.5692	$141.57	$141.55	$141.60
Purchase #4	$60.72	3.386%	$62.776	$62.78	$62.80	$62.80
Purchase #5	$202.49	10.575%	$223.9033	$223.90	$223.90	$223.90
Purchase #6	$209.51	6.729%	$223.6079	$223.61	$223.60	$223.60
Purchase #7	$183.72	4.284%	$191.5906	$191.59	$191.60	$191.60
7 purchase totals =	$1,211.04		$1,281.7646	$1,281.77	$1,281.75	$1,281.80