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	$29.75	4.816%	$31.1828	$31.18	$31.20	$31.20
Purchase #2	$183.41	4.237%	$191.1811	$191.18	$191.20	$191.20
Purchase #3	$210.86	5.704%	$222.8875	$222.89	$222.90	$222.90
Purchase #4	$65.28	11.181%	$72.579	$72.58	$72.60	$72.60
Purchase #5	$146.61	5.854%	$155.1925	$155.19	$155.20	$155.20
Purchase #6	$196.75	6.398%	$209.3381	$209.34	$209.35	$209.30
Purchase #7	$191.85	4.448%	$200.3835	$200.38	$200.40	$200.40
7 purchase totals =	$1,024.51		$1,082.7445	$1,082.74	$1,082.85	$1,082.80