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	$180.42	8.779%	$196.2591	$196.26	$196.25	$196.30
Purchase #2	$224.28	9.852%	$246.3761	$246.38	$246.40	$246.40
Purchase #3	$30.79	10.413%	$33.9962	$34.00	$34.00	$34.00
Purchase #4	$91.41	3.637%	$94.7346	$94.73	$94.75	$94.70
Purchase #5	$116.28	9.841%	$127.7231	$127.72	$127.70	$127.70
Purchase #6	$109.29	13.315%	$123.842	$123.84	$123.85	$123.80
Purchase #7	$73.26	12.669%	$82.5413	$82.54	$82.55	$82.50
7 purchase totals =	$825.73		$905.4724	$905.47	$905.50	$905.40