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	$54.98	3.254%	$56.769	$56.77	$56.75	$56.80
Purchase #2	$186.52	6.353%	$198.3696	$198.37	$198.35	$198.40
Purchase #3	$229.70	9.121%	$250.6509	$250.65	$250.65	$250.70
Purchase #4	$174.62	9.318%	$190.8911	$190.89	$190.90	$190.90
Purchase #5	$69.64	11.311%	$77.517	$77.52	$77.50	$77.50
Purchase #6	$152.91	10.667%	$169.2209	$169.22	$169.20	$169.20
Purchase #7	$156.73	9.446%	$171.5347	$171.53	$171.55	$171.50
7 purchase totals =	$1,025.10		$1,114.9532	$1,114.95	$1,114.90	$1,115.00