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	$181.66	5.431%	$191.526	$191.53	$191.55	$191.50
Purchase #2	$7.28	7.655%	$7.8373	$7.84	$7.85	$7.80
Purchase #3	$240.78	5.719%	$254.5502	$254.55	$254.55	$254.60
Purchase #4	$87.37	12.728%	$98.4905	$98.49	$98.50	$98.50
Purchase #5	$47.78	9.322%	$52.2341	$52.23	$52.25	$52.20
Purchase #6	$218.79	3.152%	$225.6863	$225.69	$225.70	$225.70
Purchase #7	$18.73	7.712%	$20.1745	$20.17	$20.15	$20.20
7 purchase totals =	$802.39		$850.4989	$850.50	$850.55	$850.50