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	$155.83	12.676%	$175.583	$175.58	$175.60	$175.60
Purchase #2	$208.51	6.646%	$222.3676	$222.37	$222.35	$222.40
Purchase #3	$222.98	5.192%	$234.5571	$234.56	$234.55	$234.60
Purchase #4	$234.36	9.488%	$256.5961	$256.60	$256.60	$256.60
Purchase #5	$34.47	3.588%	$35.7068	$35.71	$35.70	$35.70
Purchase #6	$48.40	11.214%	$53.8276	$53.83	$53.85	$53.80
Purchase #7	$144.31	8.279%	$156.2574	$156.26	$156.25	$156.30
7 purchase totals =	$1,048.86		$1,134.8956	$1,134.91	$1,134.90	$1,135.00