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	$49.56	9.171%	$54.1051	$54.11	$54.10	$54.10
Purchase #2	$154.50	11.646%	$172.4931	$172.49	$172.50	$172.50
Purchase #3	$113.55	10.401%	$125.3603	$125.36	$125.35	$125.40
Purchase #4	$54.42	3.568%	$56.3617	$56.36	$56.35	$56.40
Purchase #5	$240.96	8.492%	$261.4223	$261.42	$261.40	$261.40
Purchase #6	$97.92	11.852%	$109.5255	$109.53	$109.55	$109.50
Purchase #7	$227.80	4.511%	$238.0761	$238.08	$238.10	$238.10
7 purchase totals =	$938.71		$1,017.3441	$1,017.35	$1,017.35	$1,017.40