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	$67.71	6.719%	$72.2594	$72.26	$72.25	$72.30
Purchase #2	$47.28	8.761%	$51.4222	$51.42	$51.40	$51.40
Purchase #3	$126.51	8.717%	$137.5379	$137.54	$137.55	$137.50
Purchase #4	$162.83	12.569%	$183.2961	$183.30	$183.30	$183.30
Purchase #5	$102.39	8.706%	$111.3041	$111.30	$111.30	$111.30
Purchase #6	$250.26	7.452%	$268.9094	$268.91	$268.90	$268.90
Purchase #7	$224.26	7.342%	$240.7252	$240.73	$240.75	$240.70
7 purchase totals =	$981.24		$1,065.4543	$1,065.46	$1,065.45	$1,065.40