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	$167.56	7.385%	$179.9343	$179.93	$179.95	$179.90
Purchase #2	$21.47	8.621%	$23.3209	$23.32	$23.30	$23.30
Purchase #3	$144.25	5.560%	$152.2703	$152.27	$152.25	$152.30
Purchase #4	$85.96	7.515%	$92.4199	$92.42	$92.40	$92.40
Purchase #5	$220.80	11.116%	$245.3441	$245.34	$245.35	$245.30
Purchase #6	$135.36	5.485%	$142.7845	$142.78	$142.80	$142.80
Purchase #7	$61.31	10.586%	$67.8003	$67.80	$67.80	$67.80
7 purchase totals =	$836.71		$903.8743	$903.86	$903.85	$903.80