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	$103.42	13.644%	$117.5306	$117.53	$117.55	$117.50
Purchase #2	$207.42	13.834%	$236.1145	$236.11	$236.10	$236.10
Purchase #3	$46.61	10.323%	$51.4216	$51.42	$51.40	$51.40
Purchase #4	$222.36	12.853%	$250.9399	$250.94	$250.95	$250.90
Purchase #5	$85.91	12.296%	$96.4735	$96.47	$96.45	$96.50
Purchase #6	$56.54	12.479%	$63.5956	$63.60	$63.60	$63.60
Purchase #7	$167.25	12.760%	$188.5911	$188.59	$188.60	$188.60
7 purchase totals =	$889.51		$1,004.6668	$1,004.66	$1,004.65	$1,004.60