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	$105.66	6.675%	$112.7128	$112.71	$112.70	$112.70
Purchase #2	$110.37	11.587%	$123.1586	$123.16	$123.15	$123.20
Purchase #3	$194.42	12.528%	$218.7769	$218.78	$218.80	$218.80
Purchase #4	$228.83	5.451%	$241.3035	$241.30	$241.30	$241.30
Purchase #5	$127.75	11.280%	$142.1602	$142.16	$142.15	$142.20
Purchase #6	$31.76	7.417%	$34.1156	$34.12	$34.10	$34.10
Purchase #7	$190.39	7.328%	$204.3418	$204.34	$204.35	$204.30
7 purchase totals =	$989.18		$1,076.5694	$1,076.57	$1,076.55	$1,076.60