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	$182.61	11.438%	$203.4969	$203.50	$203.50	$203.50
Purchase #2	$245.99	13.399%	$278.9502	$278.95	$278.95	$279.00
Purchase #3	$147.32	6.472%	$156.8546	$156.85	$156.85	$156.90
Purchase #4	$121.32	4.856%	$127.2113	$127.21	$127.20	$127.20
Purchase #5	$106.67	6.676%	$113.7913	$113.79	$113.80	$113.80
Purchase #6	$52.41	9.786%	$57.5388	$57.54	$57.55	$57.50
Purchase #7	$84.59	6.172%	$89.8109	$89.81	$89.80	$89.80
7 purchase totals =	$940.91		$1,027.6540	$1,027.65	$1,027.65	$1,027.70