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	$41.38	9.508%	$45.3144	$45.31	$45.30	$45.30
Purchase #2	$246.82	3.692%	$255.9326	$255.93	$255.95	$255.90
Purchase #3	$41.55	11.512%	$46.3332	$46.33	$46.35	$46.30
Purchase #4	$174.60	5.449%	$184.114	$184.11	$184.10	$184.10
Purchase #5	$103.48	10.563%	$114.4106	$114.41	$114.40	$114.40
Purchase #6	$239.35	8.303%	$259.2232	$259.22	$259.20	$259.20
Purchase #7	$174.43	11.714%	$194.8627	$194.86	$194.85	$194.90
7 purchase totals =	$1,021.61		$1,100.1907	$1,100.17	$1,100.15	$1,100.10