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	$213.57	10.663%	$236.343	$236.34	$236.35	$236.30
Purchase #2	$29.60	7.573%	$31.8416	$31.84	$31.85	$31.80
Purchase #3	$118.94	7.718%	$128.1198	$128.12	$128.10	$128.10
Purchase #4	$210.34	11.111%	$233.7109	$233.71	$233.70	$233.70
Purchase #5	$103.93	10.271%	$114.6047	$114.60	$114.60	$114.60
Purchase #6	$39.89	7.568%	$42.9089	$42.91	$42.90	$42.90
Purchase #7	$160.32	13.230%	$181.5303	$181.53	$181.55	$181.50
7 purchase totals =	$876.59		$969.0592	$969.05	$969.05	$968.90