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	$186.34	12.829%	$210.2456	$210.25	$210.25	$210.20
Purchase #2	$146.83	10.573%	$162.3543	$162.35	$162.35	$162.40
Purchase #3	$49.69	11.284%	$55.297	$55.30	$55.30	$55.30
Purchase #4	$236.39	8.566%	$256.6392	$256.64	$256.65	$256.60
Purchase #5	$18.31	11.595%	$20.433	$20.43	$20.45	$20.40
Purchase #6	$135.40	5.499%	$142.8456	$142.85	$142.85	$142.80
Purchase #7	$117.40	3.821%	$121.8859	$121.89	$121.90	$121.90
7 purchase totals =	$890.36		$969.7006	$969.71	$969.75	$969.60