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	$97.68	8.288%	$105.7757	$105.78	$105.80	$105.80
Purchase #2	$207.92	6.822%	$222.1043	$222.10	$222.10	$222.10
Purchase #3	$217.32	11.463%	$242.2314	$242.23	$242.25	$242.20
Purchase #4	$73.93	5.742%	$78.1751	$78.18	$78.20	$78.20
Purchase #5	$184.41	5.145%	$193.8979	$193.90	$193.90	$193.90
Purchase #6	$25.58	12.486%	$28.7739	$28.77	$28.75	$28.80
Purchase #7	$162.46	13.779%	$184.8454	$184.85	$184.85	$184.80
7 purchase totals =	$969.30		$1,055.8037	$1,055.81	$1,055.85	$1,055.80