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	$67.97	10.187%	$74.8941	$74.89	$74.90	$74.90
Purchase #2	$150.31	7.869%	$162.1379	$162.14	$162.15	$162.10
Purchase #3	$40.74	4.709%	$42.6584	$42.66	$42.65	$42.70
Purchase #4	$83.84	7.803%	$90.382	$90.38	$90.40	$90.40
Purchase #5	$52.44	3.723%	$54.3923	$54.39	$54.40	$54.40
Purchase #6	$242.96	6.347%	$258.3807	$258.38	$258.40	$258.40
Purchase #7	$198.71	5.496%	$209.6311	$209.63	$209.65	$209.60
7 purchase totals =	$836.97		$892.4765	$892.47	$892.55	$892.50