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	$193.80	7.463%	$208.2633	$208.26	$208.25	$208.30
Purchase #2	$233.46	4.476%	$243.9097	$243.91	$243.90	$243.90
Purchase #3	$82.95	7.860%	$89.4699	$89.47	$89.45	$89.50
Purchase #4	$180.50	7.318%	$193.709	$193.71	$193.70	$193.70
Purchase #5	$141.86	10.127%	$156.2262	$156.23	$156.25	$156.20
Purchase #6	$38.37	6.434%	$40.8387	$40.84	$40.85	$40.80
Purchase #7	$155.96	9.448%	$170.6951	$170.70	$170.70	$170.70
7 purchase totals =	$1,026.90		$1,103.1119	$1,103.12	$1,103.10	$1,103.10