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	$103.77	13.874%	$118.167	$118.17	$118.15	$118.20
Purchase #2	$53.57	11.545%	$59.7547	$59.75	$59.75	$59.80
Purchase #3	$6.88	5.317%	$7.2458	$7.25	$7.25	$7.20
Purchase #4	$99.39	6.621%	$105.9706	$105.97	$105.95	$106.00
Purchase #5	$163.85	4.702%	$171.5542	$171.55	$171.55	$171.60
Purchase #6	$10.50	11.732%	$11.7319	$11.73	$11.75	$11.70
Purchase #7	$148.90	7.393%	$159.9082	$159.91	$159.90	$159.90
7 purchase totals =	$586.86		$634.3324	$634.33	$634.30	$634.40