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	$33.50	11.289%	$37.2818	$37.28	$37.30	$37.30
Purchase #2	$117.71	5.251%	$123.891	$123.89	$123.90	$123.90
Purchase #3	$152.44	9.158%	$166.4005	$166.40	$166.40	$166.40
Purchase #4	$115.45	4.385%	$120.5125	$120.51	$120.50	$120.50
Purchase #5	$210.92	10.178%	$232.3874	$232.39	$232.40	$232.40
Purchase #6	$185.25	10.559%	$204.8105	$204.81	$204.80	$204.80
Purchase #7	$244.81	10.124%	$269.5946	$269.59	$269.60	$269.60
7 purchase totals =	$1,060.08		$1,154.8783	$1,154.87	$1,154.90	$1,154.90