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	$224.66	8.237%	$243.1652	$243.17	$243.15	$243.20
Purchase #2	$37.93	9.653%	$41.5914	$41.59	$41.60	$41.60
Purchase #3	$151.44	3.585%	$156.8691	$156.87	$156.85	$156.90
Purchase #4	$78.99	12.460%	$88.8322	$88.83	$88.85	$88.80
Purchase #5	$215.83	5.812%	$228.374	$228.37	$228.35	$228.40
Purchase #6	$143.60	7.790%	$154.7864	$154.79	$154.80	$154.80
Purchase #7	$147.35	3.682%	$152.7754	$152.78	$152.80	$152.80
7 purchase totals =	$999.80		$1,066.3937	$1,066.40	$1,066.40	$1,066.50