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	$177.60	4.871%	$186.2509	$186.25	$186.25	$186.30
Purchase #2	$105.54	13.775%	$120.0781	$120.08	$120.10	$120.10
Purchase #3	$175.54	7.531%	$188.7599	$188.76	$188.75	$188.80
Purchase #4	$38.39	13.309%	$43.4993	$43.50	$43.50	$43.50
Purchase #5	$62.81	4.453%	$65.6069	$65.61	$65.60	$65.60
Purchase #6	$34.32	12.375%	$38.5671	$38.57	$38.55	$38.60
Purchase #7	$229.67	11.800%	$256.7711	$256.77	$256.75	$256.80
7 purchase totals =	$823.87		$899.5333	$899.54	$899.50	$899.70