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	$88.60	10.166%	$97.6071	$97.61	$97.60	$97.60
Purchase #2	$245.63	3.608%	$254.4923	$254.49	$254.50	$254.50
Purchase #3	$220.35	13.462%	$250.0135	$250.01	$250.00	$250.00
Purchase #4	$155.26	10.479%	$171.5297	$171.53	$171.55	$171.50
Purchase #5	$114.83	10.742%	$127.165	$127.17	$127.15	$127.20
Purchase #6	$250.81	8.823%	$272.939	$272.94	$272.95	$272.90
Purchase #7	$167.38	7.437%	$179.8281	$179.83	$179.85	$179.80
7 purchase totals =	$1,242.86		$1,353.5747	$1,353.58	$1,353.60	$1,353.50