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	$184.61	13.438%	$209.4179	$209.42	$209.40	$209.40
Purchase #2	$177.47	6.356%	$188.75	$188.75	$188.75	$188.80
Purchase #3	$181.43	3.844%	$188.4042	$188.40	$188.40	$188.40
Purchase #4	$93.52	13.331%	$105.9872	$105.99	$106.00	$106.00
Purchase #5	$66.76	6.350%	$70.9993	$71.00	$71.00	$71.00
Purchase #6	$89.69	13.540%	$101.834	$101.83	$101.85	$101.80
Purchase #7	$171.60	4.604%	$179.5005	$179.50	$179.50	$179.50
7 purchase totals =	$965.08		$1,044.8931	$1,044.89	$1,044.90	$1,044.90