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	$193.37	6.681%	$206.289	$206.29	$206.30	$206.30
Purchase #2	$80.25	3.196%	$82.8148	$82.81	$82.80	$82.80
Purchase #3	$185.29	10.789%	$205.2809	$205.28	$205.30	$205.30
Purchase #4	$9.83	11.393%	$10.9499	$10.95	$10.95	$10.90
Purchase #5	$158.74	10.867%	$175.9903	$175.99	$176.00	$176.00
Purchase #6	$95.71	11.269%	$106.4956	$106.50	$106.50	$106.50
Purchase #7	$102.32	6.793%	$109.2706	$109.27	$109.25	$109.30
7 purchase totals =	$825.51		$897.0911	$897.09	$897.10	$897.10