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	$130.49	9.817%	$143.3002	$143.30	$143.30	$143.30
Purchase #2	$85.26	12.762%	$96.1409	$96.14	$96.15	$96.10
Purchase #3	$102.61	6.644%	$109.4274	$109.43	$109.45	$109.40
Purchase #4	$78.97	9.304%	$86.3174	$86.32	$86.30	$86.30
Purchase #5	$65.32	8.833%	$71.0897	$71.09	$71.10	$71.10
Purchase #6	$13.86	4.844%	$14.5314	$14.53	$14.55	$14.50
Purchase #7	$145.76	6.163%	$154.7432	$154.74	$154.75	$154.70
7 purchase totals =	$622.27		$675.5502	$675.55	$675.60	$675.40