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	$210.29	8.181%	$227.4938	$227.49	$227.50	$227.50
Purchase #2	$36.41	10.349%	$40.1781	$40.18	$40.20	$40.20
Purchase #3	$181.28	13.152%	$205.1219	$205.12	$205.10	$205.10
Purchase #4	$164.32	8.134%	$177.6858	$177.69	$177.70	$177.70
Purchase #5	$19.37	11.112%	$21.5224	$21.52	$21.50	$21.50
Purchase #6	$236.32	10.697%	$261.5992	$261.60	$261.60	$261.60
Purchase #7	$145.83	3.360%	$150.7299	$150.73	$150.75	$150.70
7 purchase totals =	$993.82		$1,084.3311	$1,084.33	$1,084.35	$1,084.30