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	$103.26	3.415%	$106.7863	$106.79	$106.80	$106.80
Purchase #2	$235.32	12.734%	$265.2856	$265.29	$265.30	$265.30
Purchase #3	$66.59	5.601%	$70.3197	$70.32	$70.30	$70.30
Purchase #4	$210.98	4.828%	$221.1661	$221.17	$221.15	$221.20
Purchase #5	$152.45	4.163%	$158.7965	$158.80	$158.80	$158.80
Purchase #6	$145.90	13.278%	$165.2726	$165.27	$165.25	$165.30
Purchase #7	$114.39	4.245%	$119.2459	$119.25	$119.25	$119.20
7 purchase totals =	$1,028.89		$1,106.8727	$1,106.89	$1,106.85	$1,106.90