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	$192.28	13.352%	$217.9532	$217.95	$217.95	$218.00
Purchase #2	$175.59	6.650%	$187.2667	$187.27	$187.25	$187.30
Purchase #3	$48.96	7.761%	$52.7598	$52.76	$52.75	$52.80
Purchase #4	$127.33	3.124%	$131.3078	$131.31	$131.30	$131.30
Purchase #5	$140.73	11.229%	$156.5326	$156.53	$156.55	$156.50
Purchase #6	$94.79	4.223%	$98.793	$98.79	$98.80	$98.80
Purchase #7	$209.69	12.841%	$236.6163	$236.62	$236.60	$236.60
7 purchase totals =	$989.37		$1,081.2294	$1,081.23	$1,081.20	$1,081.30