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	$202.47	4.598%	$211.7796	$211.78	$211.80	$211.80
Purchase #2	$189.86	11.453%	$211.6047	$211.60	$211.60	$211.60
Purchase #3	$165.86	3.385%	$171.4744	$171.47	$171.45	$171.50
Purchase #4	$189.78	13.688%	$215.7571	$215.76	$215.75	$215.80
Purchase #5	$72.44	13.443%	$82.1781	$82.18	$82.20	$82.20
Purchase #6	$26.43	4.771%	$27.691	$27.69	$27.70	$27.70
Purchase #7	$115.86	13.870%	$131.9298	$131.93	$131.95	$131.90
7 purchase totals =	$962.70		$1,052.4147	$1,052.41	$1,052.45	$1,052.50