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	$237.41	5.240%	$249.8503	$249.85	$249.85	$249.90
Purchase #2	$130.29	3.143%	$134.385	$134.39	$134.40	$134.40
Purchase #3	$83.33	7.840%	$89.8631	$89.86	$89.85	$89.90
Purchase #4	$215.88	4.376%	$225.3269	$225.33	$225.35	$225.30
Purchase #5	$19.44	4.304%	$20.2767	$20.28	$20.30	$20.30
Purchase #6	$224.84	10.834%	$249.1992	$249.20	$249.20	$249.20
Purchase #7	$72.47	4.707%	$75.8812	$75.88	$75.90	$75.90
7 purchase totals =	$983.66		$1,044.7824	$1,044.79	$1,044.85	$1,044.90