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	$193.29	11.607%	$215.7252	$215.73	$215.75	$215.70
Purchase #2	$25.79	10.628%	$28.531	$28.53	$28.55	$28.50
Purchase #3	$149.98	11.592%	$167.3657	$167.37	$167.35	$167.40
Purchase #4	$216.41	5.860%	$229.0916	$229.09	$229.10	$229.10
Purchase #5	$241.98	10.586%	$267.596	$267.60	$267.60	$267.60
Purchase #6	$150.38	9.236%	$164.2691	$164.27	$164.25	$164.30
Purchase #7	$131.50	9.868%	$144.4764	$144.48	$144.50	$144.50
7 purchase totals =	$1,109.33		$1,217.0550	$1,217.07	$1,217.10	$1,217.10