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	$82.93	11.146%	$92.1734	$92.17	$92.15	$92.20
Purchase #2	$151.40	7.608%	$162.9185	$162.92	$162.90	$162.90
Purchase #3	$99.41	3.811%	$103.1985	$103.20	$103.20	$103.20
Purchase #4	$31.83	11.235%	$35.4061	$35.41	$35.40	$35.40
Purchase #5	$155.76	11.849%	$174.216	$174.22	$174.20	$174.20
Purchase #6	$126.29	10.501%	$139.5517	$139.55	$139.55	$139.60
Purchase #7	$11.71	10.125%	$12.8956	$12.90	$12.90	$12.90
7 purchase totals =	$659.33		$720.3598	$720.37	$720.30	$720.40