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	$42.91	10.502%	$47.4164	$47.42	$47.40	$47.40
Purchase #2	$236.39	7.251%	$253.5306	$253.53	$253.55	$253.50
Purchase #3	$137.79	10.549%	$152.3255	$152.33	$152.35	$152.30
Purchase #4	$160.37	3.266%	$165.6077	$165.61	$165.60	$165.60
Purchase #5	$145.65	10.252%	$160.582	$160.58	$160.60	$160.60
Purchase #6	$62.58	3.274%	$64.6289	$64.63	$64.65	$64.60
Purchase #7	$167.64	11.831%	$187.4735	$187.47	$187.45	$187.50
7 purchase totals =	$953.33		$1,031.5646	$1,031.57	$1,031.60	$1,031.50