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	$53.39	4.108%	$55.5833	$55.58	$55.60	$55.60
Purchase #2	$64.85	13.606%	$73.6735	$73.67	$73.65	$73.70
Purchase #3	$99.76	5.741%	$105.4872	$105.49	$105.50	$105.50
Purchase #4	$243.82	8.811%	$265.303	$265.30	$265.30	$265.30
Purchase #5	$163.33	10.755%	$180.8961	$180.90	$180.90	$180.90
Purchase #6	$81.52	12.446%	$91.666	$91.67	$91.65	$91.70
Purchase #7	$8.56	3.482%	$8.8581	$8.86	$8.85	$8.90
7 purchase totals =	$715.23		$781.4672	$781.47	$781.45	$781.60