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	$149.64	6.677%	$159.6315	$159.63	$159.65	$159.60
Purchase #2	$86.33	4.339%	$90.0759	$90.08	$90.10	$90.10
Purchase #3	$22.61	11.697%	$25.2547	$25.25	$25.25	$25.30
Purchase #4	$63.39	4.222%	$66.0663	$66.07	$66.05	$66.10
Purchase #5	$101.62	10.543%	$112.3338	$112.33	$112.35	$112.30
Purchase #6	$167.51	11.674%	$187.0651	$187.07	$187.05	$187.10
Purchase #7	$169.28	9.554%	$185.453	$185.45	$185.45	$185.50
7 purchase totals =	$760.38		$825.8803	$825.88	$825.90	$826.00