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	$224.79	6.211%	$238.7517	$238.75	$238.75	$238.80
Purchase #2	$216.98	7.654%	$233.5876	$233.59	$233.60	$233.60
Purchase #3	$205.45	11.138%	$228.333	$228.33	$228.35	$228.30
Purchase #4	$63.69	11.113%	$70.7679	$70.77	$70.75	$70.80
Purchase #5	$65.76	11.119%	$73.0719	$73.07	$73.05	$73.10
Purchase #6	$211.76	13.537%	$240.426	$240.43	$240.45	$240.40
Purchase #7	$18.58	8.346%	$20.1307	$20.13	$20.15	$20.10
7 purchase totals =	$1,007.01		$1,105.0688	$1,105.07	$1,105.10	$1,105.10