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	$177.94	10.282%	$196.2358	$196.24	$196.25	$196.20
Purchase #2	$171.69	10.672%	$190.0128	$190.01	$190.00	$190.00
Purchase #3	$70.49	13.621%	$80.0914	$80.09	$80.10	$80.10
Purchase #4	$99.51	7.450%	$106.9235	$106.92	$106.90	$106.90
Purchase #5	$159.88	10.498%	$176.6642	$176.66	$176.65	$176.70
Purchase #6	$139.85	9.193%	$152.7064	$152.71	$152.70	$152.70
Purchase #7	$182.56	6.431%	$194.3004	$194.30	$194.30	$194.30
7 purchase totals =	$1,001.92		$1,096.9345	$1,096.93	$1,096.90	$1,096.90