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	$34.36	7.726%	$37.0147	$37.01	$37.00	$37.00
Purchase #2	$13.69	6.118%	$14.5276	$14.53	$14.55	$14.50
Purchase #3	$216.71	8.792%	$235.7631	$235.76	$235.75	$235.80
Purchase #4	$167.93	8.155%	$181.6247	$181.62	$181.60	$181.60
Purchase #5	$190.61	10.378%	$210.3915	$210.39	$210.40	$210.40
Purchase #6	$90.39	6.761%	$96.5013	$96.50	$96.50	$96.50
Purchase #7	$203.70	12.131%	$228.4108	$228.41	$228.40	$228.40
7 purchase totals =	$917.39		$1,004.2337	$1,004.22	$1,004.20	$1,004.20