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	$179.57	5.494%	$189.4356	$189.44	$189.45	$189.40
Purchase #2	$96.32	5.161%	$101.2911	$101.29	$101.30	$101.30
Purchase #3	$211.52	5.775%	$223.7353	$223.74	$223.75	$223.70
Purchase #4	$154.27	11.780%	$172.443	$172.44	$172.45	$172.40
Purchase #5	$185.61	3.222%	$191.5904	$191.59	$191.60	$191.60
Purchase #6	$31.59	13.550%	$35.8704	$35.87	$35.85	$35.90
Purchase #7	$108.82	12.122%	$122.0112	$122.01	$122.00	$122.00
7 purchase totals =	$967.70		$1,036.3770	$1,036.38	$1,036.40	$1,036.30