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	$210.83	3.581%	$218.3798	$218.38	$218.40	$218.40
Purchase #2	$167.65	12.329%	$188.3196	$188.32	$188.30	$188.30
Purchase #3	$246.83	5.727%	$260.966	$260.97	$260.95	$261.00
Purchase #4	$86.54	3.368%	$89.4547	$89.45	$89.45	$89.50
Purchase #5	$57.50	13.651%	$65.3493	$65.35	$65.35	$65.30
Purchase #6	$68.72	3.518%	$71.1376	$71.14	$71.15	$71.10
Purchase #7	$180.34	5.385%	$190.0513	$190.05	$190.05	$190.10
7 purchase totals =	$1,018.41		$1,083.6583	$1,083.66	$1,083.65	$1,083.70