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	$209.70	10.426%	$231.5633	$231.56	$231.55	$231.60
Purchase #2	$229.52	10.113%	$252.7314	$252.73	$252.75	$252.70
Purchase #3	$41.35	11.529%	$46.1172	$46.12	$46.10	$46.10
Purchase #4	$89.60	5.606%	$94.623	$94.62	$94.60	$94.60
Purchase #5	$224.80	7.478%	$241.6105	$241.61	$241.60	$241.60
Purchase #6	$100.92	8.313%	$109.3095	$109.31	$109.30	$109.30
Purchase #7	$40.33	4.818%	$42.2731	$42.27	$42.25	$42.30
7 purchase totals =	$936.22		$1,018.2280	$1,018.22	$1,018.15	$1,018.20