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	$228.71	4.206%	$238.3295	$238.33	$238.35	$238.30
Purchase #2	$175.72	7.736%	$189.3137	$189.31	$189.30	$189.30
Purchase #3	$94.36	7.512%	$101.4483	$101.45	$101.45	$101.40
Purchase #4	$154.72	9.575%	$169.5344	$169.53	$169.55	$169.50
Purchase #5	$111.81	10.215%	$123.2314	$123.23	$123.25	$123.20
Purchase #6	$194.29	9.609%	$212.9593	$212.96	$212.95	$213.00
Purchase #7	$151.92	6.228%	$161.3816	$161.38	$161.40	$161.40
7 purchase totals =	$1,111.53		$1,196.1982	$1,196.19	$1,196.25	$1,196.10