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	$195.48	8.406%	$211.912	$211.91	$211.90	$211.90
Purchase #2	$168.57	10.568%	$186.3845	$186.38	$186.40	$186.40
Purchase #3	$159.50	13.167%	$180.5014	$180.50	$180.50	$180.50
Purchase #4	$72.69	12.254%	$81.5974	$81.60	$81.60	$81.60
Purchase #5	$147.54	13.465%	$167.4063	$167.41	$167.40	$167.40
Purchase #6	$65.29	10.442%	$72.1076	$72.11	$72.10	$72.10
Purchase #7	$142.36	3.684%	$147.6045	$147.60	$147.60	$147.60
7 purchase totals =	$951.43		$1,047.5137	$1,047.51	$1,047.50	$1,047.50