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	$169.78	9.147%	$185.3098	$185.31	$185.30	$185.30
Purchase #2	$168.39	10.130%	$185.4479	$185.45	$185.45	$185.40
Purchase #3	$41.39	7.556%	$44.5174	$44.52	$44.50	$44.50
Purchase #4	$113.76	10.586%	$125.8026	$125.80	$125.80	$125.80
Purchase #5	$119.85	3.289%	$123.7919	$123.79	$123.80	$123.80
Purchase #6	$18.62	9.224%	$20.3375	$20.34	$20.35	$20.30
Purchase #7	$103.26	10.137%	$113.7275	$113.73	$113.75	$113.70
7 purchase totals =	$735.05		$798.9346	$798.94	$798.95	$798.80