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	$51.42	3.177%	$53.0536	$53.05	$53.05	$53.10
Purchase #2	$95.54	10.356%	$105.4341	$105.43	$105.45	$105.40
Purchase #3	$237.92	3.231%	$245.6072	$245.61	$245.60	$245.60
Purchase #4	$216.39	5.118%	$227.4648	$227.46	$227.45	$227.50
Purchase #5	$95.50	4.110%	$99.4251	$99.43	$99.45	$99.40
Purchase #6	$220.90	7.623%	$237.7392	$237.74	$237.75	$237.70
Purchase #7	$78.80	3.530%	$81.5816	$81.58	$81.60	$81.60
7 purchase totals =	$996.47		$1,050.3056	$1,050.30	$1,050.35	$1,050.30