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	$65.27	8.572%	$70.8649	$70.86	$70.85	$70.90
Purchase #2	$103.91	9.263%	$113.5352	$113.54	$113.55	$113.50
Purchase #3	$18.47	11.427%	$20.5806	$20.58	$20.60	$20.60
Purchase #4	$180.71	6.439%	$192.3459	$192.35	$192.35	$192.30
Purchase #5	$219.31	3.288%	$226.5209	$226.52	$226.50	$226.50
Purchase #6	$216.97	11.861%	$242.7048	$242.70	$242.70	$242.70
Purchase #7	$127.97	11.791%	$143.0589	$143.06	$143.05	$143.10
7 purchase totals =	$932.61		$1,009.6112	$1,009.61	$1,009.60	$1,009.60