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	$26.92	4.803%	$28.213	$28.21	$28.20	$28.20
Purchase #2	$176.88	5.111%	$185.9203	$185.92	$185.90	$185.90
Purchase #3	$91.52	10.227%	$100.8798	$100.88	$100.90	$100.90
Purchase #4	$196.96	8.566%	$213.8316	$213.83	$213.85	$213.80
Purchase #5	$173.89	6.305%	$184.8538	$184.85	$184.85	$184.90
Purchase #6	$91.97	13.541%	$104.4237	$104.42	$104.40	$104.40
Purchase #7	$17.54	6.844%	$18.7404	$18.74	$18.75	$18.70
7 purchase totals =	$775.68		$836.8626	$836.85	$836.85	$836.80