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	$220.93	9.636%	$242.2188	$242.22	$242.20	$242.20
Purchase #2	$55.39	6.865%	$59.1925	$59.19	$59.20	$59.20
Purchase #3	$11.38	3.530%	$11.7817	$11.78	$11.80	$11.80
Purchase #4	$176.89	7.215%	$189.6526	$189.65	$189.65	$189.70
Purchase #5	$137.29	13.797%	$156.2319	$156.23	$156.25	$156.20
Purchase #6	$109.93	11.797%	$122.8984	$122.90	$122.90	$122.90
Purchase #7	$214.74	9.148%	$234.3844	$234.38	$234.40	$234.40
7 purchase totals =	$926.55		$1,016.3603	$1,016.35	$1,016.40	$1,016.40