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	$205.74	6.604%	$219.3271	$219.33	$219.35	$219.30
Purchase #2	$202.86	11.279%	$225.7406	$225.74	$225.75	$225.70
Purchase #3	$250.82	11.194%	$278.8968	$278.90	$278.90	$278.90
Purchase #4	$87.86	4.524%	$91.8348	$91.83	$91.85	$91.80
Purchase #5	$180.68	3.707%	$187.3778	$187.38	$187.40	$187.40
Purchase #6	$209.74	6.103%	$222.5404	$222.54	$222.55	$222.50
Purchase #7	$6.78	13.542%	$7.6981	$7.70	$7.70	$7.70
7 purchase totals =	$1,144.48		$1,233.4156	$1,233.42	$1,233.50	$1,233.30