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	$69.53	12.570%	$78.2699	$78.27	$78.25	$78.30
Purchase #2	$36.90	11.732%	$41.2291	$41.23	$41.25	$41.20
Purchase #3	$60.79	9.288%	$66.4362	$66.44	$66.45	$66.40
Purchase #4	$127.40	9.170%	$139.0826	$139.08	$139.10	$139.10
Purchase #5	$56.25	11.451%	$62.6912	$62.69	$62.70	$62.70
Purchase #6	$103.84	5.168%	$109.2065	$109.21	$109.20	$109.20
Purchase #7	$246.52	4.146%	$256.7407	$256.74	$256.75	$256.70
7 purchase totals =	$701.23		$753.6562	$753.66	$753.70	$753.60