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	$118.38	7.654%	$127.4408	$127.44	$127.45	$127.40
Purchase #2	$210.45	5.842%	$222.7445	$222.74	$222.75	$222.70
Purchase #3	$137.84	13.206%	$156.0432	$156.04	$156.05	$156.00
Purchase #4	$240.79	6.647%	$256.7953	$256.80	$256.80	$256.80
Purchase #5	$41.95	10.154%	$46.2096	$46.21	$46.20	$46.20
Purchase #6	$30.66	8.474%	$33.2581	$33.26	$33.25	$33.30
Purchase #7	$228.96	11.120%	$254.4204	$254.42	$254.40	$254.40
7 purchase totals =	$1,009.03		$1,096.9119	$1,096.91	$1,096.90	$1,096.80