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	$112.29	9.596%	$123.0653	$123.07	$123.05	$123.10
Purchase #2	$142.44	9.556%	$156.0516	$156.05	$156.05	$156.10
Purchase #3	$43.28	13.696%	$49.2076	$49.21	$49.20	$49.20
Purchase #4	$190.37	13.197%	$215.4931	$215.49	$215.50	$215.50
Purchase #5	$130.60	4.778%	$136.8401	$136.84	$136.85	$136.80
Purchase #6	$94.41	12.560%	$106.2679	$106.27	$106.25	$106.30
Purchase #7	$105.91	3.276%	$109.3796	$109.38	$109.40	$109.40
7 purchase totals =	$819.30		$896.3052	$896.31	$896.30	$896.40