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	$118.90	7.764%	$128.1314	$128.13	$128.15	$128.10
Purchase #2	$40.30	7.665%	$43.389	$43.39	$43.40	$43.40
Purchase #3	$116.45	3.145%	$120.1124	$120.11	$120.10	$120.10
Purchase #4	$168.87	11.158%	$187.7125	$187.71	$187.70	$187.70
Purchase #5	$9.97	3.331%	$10.3021	$10.30	$10.30	$10.30
Purchase #6	$138.55	7.170%	$148.484	$148.48	$148.50	$148.50
Purchase #7	$154.51	11.689%	$172.5707	$172.57	$172.55	$172.60
7 purchase totals =	$747.55		$810.7021	$810.69	$810.70	$810.70