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	$249.94	9.272%	$273.1144	$273.11	$273.10	$273.10
Purchase #2	$207.72	9.812%	$228.1015	$228.10	$228.10	$228.10
Purchase #3	$37.34	9.649%	$40.9429	$40.94	$40.95	$40.90
Purchase #4	$249.84	6.745%	$266.6917	$266.69	$266.70	$266.70
Purchase #5	$39.60	9.276%	$43.2733	$43.27	$43.25	$43.30
Purchase #6	$48.36	13.126%	$54.7077	$54.71	$54.70	$54.70
Purchase #7	$167.44	4.457%	$174.9028	$174.90	$174.90	$174.90
7 purchase totals =	$1,000.24		$1,081.7343	$1,081.72	$1,081.70	$1,081.70