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	$167.90	12.451%	$188.8052	$188.81	$188.80	$188.80
Purchase #2	$189.30	7.665%	$203.8098	$203.81	$203.80	$203.80
Purchase #3	$55.35	6.790%	$59.1083	$59.11	$59.10	$59.10
Purchase #4	$145.51	9.106%	$158.7601	$158.76	$158.75	$158.80
Purchase #5	$196.75	6.376%	$209.2948	$209.29	$209.30	$209.30
Purchase #6	$109.88	3.228%	$113.4269	$113.43	$113.45	$113.40
Purchase #7	$86.48	6.592%	$92.1808	$92.18	$92.20	$92.20
7 purchase totals =	$951.17		$1,025.3859	$1,025.39	$1,025.40	$1,025.40