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	$182.36	13.608%	$207.1755	$207.18	$207.20	$207.20
Purchase #2	$38.29	13.585%	$43.4917	$43.49	$43.50	$43.50
Purchase #3	$78.42	5.546%	$82.7692	$82.77	$82.75	$82.80
Purchase #4	$102.37	7.170%	$109.7099	$109.71	$109.70	$109.70
Purchase #5	$80.69	13.464%	$91.5541	$91.55	$91.55	$91.60
Purchase #6	$150.41	11.343%	$167.471	$167.47	$167.45	$167.50
Purchase #7	$41.47	8.530%	$45.0074	$45.01	$45.00	$45.00
7 purchase totals =	$674.01		$747.1788	$747.18	$747.15	$747.30