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	$172.86	6.479%	$184.0596	$184.06	$184.05	$184.10
Purchase #2	$227.89	8.355%	$246.9302	$246.93	$246.95	$246.90
Purchase #3	$139.47	9.625%	$152.894	$152.89	$152.90	$152.90
Purchase #4	$94.88	4.377%	$99.0329	$99.03	$99.05	$99.00
Purchase #5	$99.40	9.740%	$109.0816	$109.08	$109.10	$109.10
Purchase #6	$82.35	11.137%	$91.5213	$91.52	$91.50	$91.50
Purchase #7	$176.73	6.692%	$188.5568	$188.56	$188.55	$188.60
7 purchase totals =	$993.58		$1,072.0764	$1,072.07	$1,072.10	$1,072.10