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	$173.91	13.191%	$196.8505	$196.85	$196.85	$196.90
Purchase #2	$102.52	11.119%	$113.9192	$113.92	$113.90	$113.90
Purchase #3	$109.87	12.370%	$123.4609	$123.46	$123.45	$123.50
Purchase #4	$137.93	3.804%	$143.1769	$143.18	$143.20	$143.20
Purchase #5	$185.32	13.421%	$210.1918	$210.19	$210.20	$210.20
Purchase #6	$11.71	8.710%	$12.7299	$12.73	$12.75	$12.70
Purchase #7	$69.56	6.364%	$73.9868	$73.99	$74.00	$74.00
7 purchase totals =	$790.82		$874.3160	$874.32	$874.35	$874.40