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	$99.81	6.158%	$105.9563	$105.96	$105.95	$106.00
Purchase #2	$218.49	11.343%	$243.2733	$243.27	$243.25	$243.30
Purchase #3	$137.47	5.417%	$144.9167	$144.92	$144.90	$144.90
Purchase #4	$106.78	4.197%	$111.2616	$111.26	$111.25	$111.30
Purchase #5	$237.36	8.205%	$256.8354	$256.84	$256.85	$256.80
Purchase #6	$157.70	9.151%	$172.1311	$172.13	$172.15	$172.10
Purchase #7	$54.31	13.432%	$61.6049	$61.60	$61.60	$61.60
7 purchase totals =	$1,011.92		$1,095.9793	$1,095.98	$1,095.95	$1,096.00