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	$64.48	10.481%	$71.2381	$71.24	$71.25	$71.20
Purchase #2	$97.78	11.546%	$109.0697	$109.07	$109.05	$109.10
Purchase #3	$205.89	6.601%	$219.4808	$219.48	$219.50	$219.50
Purchase #4	$198.40	6.747%	$211.786	$211.79	$211.80	$211.80
Purchase #5	$97.25	13.527%	$110.405	$110.41	$110.40	$110.40
Purchase #6	$117.96	4.480%	$123.2446	$123.24	$123.25	$123.20
Purchase #7	$217.42	5.335%	$229.0194	$229.02	$229.00	$229.00
7 purchase totals =	$999.18		$1,074.2436	$1,074.25	$1,074.25	$1,074.20