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	$20.78	7.319%	$22.3009	$22.30	$22.30	$22.30
Purchase #2	$89.44	5.324%	$94.2018	$94.20	$94.20	$94.20
Purchase #3	$155.56	10.187%	$171.4069	$171.41	$171.40	$171.40
Purchase #4	$157.34	9.767%	$172.7074	$172.71	$172.70	$172.70
Purchase #5	$199.40	11.276%	$221.8843	$221.88	$221.90	$221.90
Purchase #6	$239.60	10.764%	$265.3905	$265.39	$265.40	$265.40
Purchase #7	$81.84	9.843%	$89.8955	$89.90	$89.90	$89.90
7 purchase totals =	$943.96		$1,037.7873	$1,037.79	$1,037.80	$1,037.80