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	$219.35	7.753%	$236.3562	$236.36	$236.35	$236.40
Purchase #2	$181.94	10.324%	$200.7235	$200.72	$200.70	$200.70
Purchase #3	$179.98	11.139%	$200.028	$200.03	$200.05	$200.00
Purchase #4	$112.57	7.388%	$120.8867	$120.89	$120.90	$120.90
Purchase #5	$80.62	7.698%	$86.8261	$86.83	$86.85	$86.80
Purchase #6	$221.84	6.846%	$237.0272	$237.03	$237.05	$237.00
Purchase #7	$53.82	11.403%	$59.9571	$59.96	$59.95	$60.00
7 purchase totals =	$1,050.12		$1,141.8048	$1,141.82	$1,141.85	$1,141.80