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	$146.36	11.253%	$162.8299	$162.83	$162.85	$162.80
Purchase #2	$128.48	4.718%	$134.5417	$134.54	$134.55	$134.50
Purchase #3	$174.67	4.856%	$183.152	$183.15	$183.15	$183.20
Purchase #4	$219.89	12.671%	$247.7523	$247.75	$247.75	$247.80
Purchase #5	$14.42	7.800%	$15.5448	$15.54	$15.55	$15.50
Purchase #6	$131.73	7.806%	$142.0128	$142.01	$142.00	$142.00
Purchase #7	$249.61	13.710%	$283.8315	$283.83	$283.85	$283.80
7 purchase totals =	$1,065.16		$1,169.6650	$1,169.65	$1,169.70	$1,169.60