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	$193.85	8.803%	$210.9146	$210.91	$210.90	$210.90
Purchase #2	$57.54	8.737%	$62.5673	$62.57	$62.55	$62.60
Purchase #3	$79.63	3.362%	$82.3072	$82.31	$82.30	$82.30
Purchase #4	$21.35	12.799%	$24.0826	$24.08	$24.10	$24.10
Purchase #5	$78.35	13.825%	$89.1819	$89.18	$89.20	$89.20
Purchase #6	$72.81	11.660%	$81.2996	$81.30	$81.30	$81.30
Purchase #7	$103.73	13.830%	$118.0759	$118.08	$118.10	$118.10
7 purchase totals =	$607.26		$668.4291	$668.43	$668.45	$668.50