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	$158.92	11.566%	$177.3007	$177.30	$177.30	$177.30
Purchase #2	$73.56	12.715%	$82.9132	$82.91	$82.90	$82.90
Purchase #3	$188.41	3.645%	$195.2775	$195.28	$195.30	$195.30
Purchase #4	$116.69	11.794%	$130.4524	$130.45	$130.45	$130.50
Purchase #5	$46.54	4.192%	$48.491	$48.49	$48.50	$48.50
Purchase #6	$128.59	4.791%	$134.7507	$134.75	$134.75	$134.80
Purchase #7	$75.83	8.583%	$82.3385	$82.34	$82.35	$82.30
7 purchase totals =	$788.54		$851.5240	$851.52	$851.55	$851.60