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	$70.97	3.418%	$73.3958	$73.40	$73.40	$73.40
Purchase #2	$101.38	7.824%	$109.312	$109.31	$109.30	$109.30
Purchase #3	$250.44	4.585%	$261.9227	$261.92	$261.90	$261.90
Purchase #4	$225.38	7.596%	$242.4999	$242.50	$242.50	$242.50
Purchase #5	$136.80	10.706%	$151.4458	$151.45	$151.45	$151.40
Purchase #6	$11.54	6.424%	$12.2813	$12.28	$12.30	$12.30
Purchase #7	$17.74	4.142%	$18.4748	$18.47	$18.45	$18.50
7 purchase totals =	$814.25		$869.3323	$869.33	$869.30	$869.30