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	$231.47	5.288%	$243.7101	$243.71	$243.70	$243.70
Purchase #2	$229.56	10.433%	$253.51	$253.51	$253.50	$253.50
Purchase #3	$203.59	9.785%	$223.5113	$223.51	$223.50	$223.50
Purchase #4	$96.94	12.744%	$109.294	$109.29	$109.30	$109.30
Purchase #5	$183.56	3.165%	$189.3697	$189.37	$189.35	$189.40
Purchase #6	$102.53	4.255%	$106.8927	$106.89	$106.90	$106.90
Purchase #7	$38.92	10.305%	$42.9307	$42.93	$42.95	$42.90
7 purchase totals =	$1,086.57		$1,169.2185	$1,169.21	$1,169.20	$1,169.20