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	$168.73	10.619%	$186.6474	$186.65	$186.65	$186.60
Purchase #2	$221.74	9.336%	$242.4416	$242.44	$242.45	$242.40
Purchase #3	$145.39	4.832%	$152.4152	$152.42	$152.40	$152.40
Purchase #4	$128.39	12.557%	$144.5119	$144.51	$144.50	$144.50
Purchase #5	$241.86	12.687%	$272.5448	$272.54	$272.55	$272.50
Purchase #6	$40.83	10.709%	$45.2025	$45.20	$45.20	$45.20
Purchase #7	$166.56	8.274%	$180.3412	$180.34	$180.35	$180.30
7 purchase totals =	$1,113.50		$1,224.1046	$1,224.10	$1,224.10	$1,223.90