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	$151.29	3.259%	$156.2205	$156.22	$156.20	$156.20
Purchase #2	$178.79	10.521%	$197.6005	$197.60	$197.60	$197.60
Purchase #3	$112.35	11.704%	$125.4994	$125.50	$125.50	$125.50
Purchase #4	$212.75	7.359%	$228.4063	$228.41	$228.40	$228.40
Purchase #5	$85.64	5.338%	$90.2115	$90.21	$90.20	$90.20
Purchase #6	$115.30	6.842%	$123.1888	$123.19	$123.20	$123.20
Purchase #7	$216.77	12.279%	$243.3872	$243.39	$243.40	$243.40
7 purchase totals =	$1,072.89		$1,164.5142	$1,164.52	$1,164.50	$1,164.50