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	$143.76	13.727%	$163.4939	$163.49	$163.50	$163.50
Purchase #2	$206.86	13.658%	$235.1129	$235.11	$235.10	$235.10
Purchase #3	$76.53	9.371%	$83.7016	$83.70	$83.70	$83.70
Purchase #4	$80.73	11.136%	$89.7201	$89.72	$89.70	$89.70
Purchase #5	$105.64	3.503%	$109.3406	$109.34	$109.35	$109.30
Purchase #6	$156.35	5.131%	$164.3723	$164.37	$164.35	$164.40
Purchase #7	$116.64	10.407%	$128.7787	$128.78	$128.80	$128.80
7 purchase totals =	$886.51		$974.5201	$974.51	$974.50	$974.50