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	$185.78	8.678%	$201.902	$201.90	$201.90	$201.90
Purchase #2	$183.96	10.123%	$202.5823	$202.58	$202.60	$202.60
Purchase #3	$30.73	4.623%	$32.1506	$32.15	$32.15	$32.20
Purchase #4	$89.71	10.443%	$99.0784	$99.08	$99.10	$99.10
Purchase #5	$209.48	13.830%	$238.4511	$238.45	$238.45	$238.50
Purchase #6	$166.27	10.585%	$183.8697	$183.87	$183.85	$183.90
Purchase #7	$205.47	4.867%	$215.4702	$215.47	$215.45	$215.50
7 purchase totals =	$1,071.40		$1,173.5043	$1,173.50	$1,173.50	$1,173.70