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	$91.46	11.205%	$101.7081	$101.71	$101.70	$101.70
Purchase #2	$207.98	5.378%	$219.1652	$219.17	$219.15	$219.20
Purchase #3	$130.29	8.304%	$141.1093	$141.11	$141.10	$141.10
Purchase #4	$84.83	8.476%	$92.0202	$92.02	$92.00	$92.00
Purchase #5	$119.55	3.548%	$123.7916	$123.79	$123.80	$123.80
Purchase #6	$158.31	4.508%	$165.4466	$165.45	$165.45	$165.40
Purchase #7	$207.48	8.691%	$225.5121	$225.51	$225.50	$225.50
7 purchase totals =	$999.90		$1,068.7531	$1,068.76	$1,068.70	$1,068.70