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	$168.39	11.845%	$188.3358	$188.34	$188.35	$188.30
Purchase #2	$177.26	13.125%	$200.5254	$200.53	$200.55	$200.50
Purchase #3	$191.51	8.812%	$208.3859	$208.39	$208.40	$208.40
Purchase #4	$14.84	4.464%	$15.5025	$15.50	$15.50	$15.50
Purchase #5	$31.78	6.256%	$33.7682	$33.77	$33.75	$33.80
Purchase #6	$241.73	5.868%	$255.9147	$255.91	$255.90	$255.90
Purchase #7	$162.86	10.123%	$179.3463	$179.35	$179.35	$179.30
7 purchase totals =	$988.37		$1,081.7788	$1,081.79	$1,081.80	$1,081.70