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	$99.58	10.321%	$109.8577	$109.86	$109.85	$109.90
Purchase #2	$181.29	9.431%	$198.3875	$198.39	$198.40	$198.40
Purchase #3	$224.40	9.333%	$245.3433	$245.34	$245.35	$245.30
Purchase #4	$35.78	4.871%	$37.5228	$37.52	$37.50	$37.50
Purchase #5	$234.61	13.509%	$266.3035	$266.30	$266.30	$266.30
Purchase #6	$224.66	7.424%	$241.3388	$241.34	$241.35	$241.30
Purchase #7	$26.42	10.839%	$29.2837	$29.28	$29.30	$29.30
7 purchase totals =	$1,026.74		$1,128.0373	$1,128.03	$1,128.05	$1,128.00