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	$94.42	13.495%	$107.162	$107.16	$107.15	$107.20
Purchase #2	$134.89	9.377%	$147.5386	$147.54	$147.55	$147.50
Purchase #3	$218.68	11.514%	$243.8588	$243.86	$243.85	$243.90
Purchase #4	$166.54	12.241%	$186.9262	$186.93	$186.95	$186.90
Purchase #5	$165.79	11.858%	$185.4494	$185.45	$185.45	$185.40
Purchase #6	$178.84	6.454%	$190.3823	$190.38	$190.40	$190.40
Purchase #7	$36.89	7.199%	$39.5457	$39.55	$39.55	$39.50
7 purchase totals =	$996.05		$1,100.8630	$1,100.87	$1,100.90	$1,100.80