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	$186.36	3.810%	$193.4603	$193.46	$193.45	$193.50
Purchase #2	$36.72	5.836%	$38.863	$38.86	$38.85	$38.90
Purchase #3	$134.89	11.375%	$150.2337	$150.23	$150.25	$150.20
Purchase #4	$34.59	3.850%	$35.9217	$35.92	$35.90	$35.90
Purchase #5	$89.46	12.621%	$100.7507	$100.75	$100.75	$100.80
Purchase #6	$58.68	11.507%	$65.4323	$65.43	$65.45	$65.40
Purchase #7	$128.63	6.247%	$136.6655	$136.67	$136.65	$136.70
7 purchase totals =	$669.33		$721.3272	$721.32	$721.30	$721.40