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	$219.88	3.679%	$227.9694	$227.97	$227.95	$228.00
Purchase #2	$127.88	7.532%	$137.5119	$137.51	$137.50	$137.50
Purchase #3	$179.94	3.160%	$185.6261	$185.63	$185.65	$185.60
Purchase #4	$239.63	12.357%	$269.2411	$269.24	$269.25	$269.20
Purchase #5	$151.73	5.133%	$159.5183	$159.52	$159.50	$159.50
Purchase #6	$41.62	5.245%	$43.803	$43.80	$43.80	$43.80
Purchase #7	$100.27	13.651%	$113.9579	$113.96	$113.95	$114.00
7 purchase totals =	$1,060.95		$1,137.6277	$1,137.63	$1,137.60	$1,137.60