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	$140.36	9.280%	$153.3854	$153.39	$153.40	$153.40
Purchase #2	$89.46	7.142%	$95.8492	$95.85	$95.85	$95.80
Purchase #3	$88.36	13.219%	$100.0403	$100.04	$100.05	$100.00
Purchase #4	$75.94	3.488%	$78.5888	$78.59	$78.60	$78.60
Purchase #5	$240.35	11.232%	$267.3461	$267.35	$267.35	$267.30
Purchase #6	$242.50	3.632%	$251.3076	$251.31	$251.30	$251.30
Purchase #7	$174.90	7.549%	$188.1032	$188.10	$188.10	$188.10
7 purchase totals =	$1,051.87		$1,134.6206	$1,134.63	$1,134.65	$1,134.50