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	$182.91	9.712%	$200.6742	$200.67	$200.65	$200.70
Purchase #2	$49.79	8.215%	$53.8802	$53.88	$53.90	$53.90
Purchase #3	$28.85	12.513%	$32.46	$32.46	$32.45	$32.50
Purchase #4	$116.89	12.568%	$131.5807	$131.58	$131.60	$131.60
Purchase #5	$21.83	10.552%	$24.1335	$24.13	$24.15	$24.10
Purchase #6	$217.41	6.775%	$232.1395	$232.14	$232.15	$232.10
Purchase #7	$173.56	10.188%	$191.2423	$191.24	$191.25	$191.20
7 purchase totals =	$791.24		$866.1104	$866.10	$866.15	$866.10