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	$171.97	8.469%	$186.5341	$186.53	$186.55	$186.50
Purchase #2	$171.63	11.176%	$190.8114	$190.81	$190.80	$190.80
Purchase #3	$233.37	6.651%	$248.8914	$248.89	$248.90	$248.90
Purchase #4	$161.73	10.113%	$178.0858	$178.09	$178.10	$178.10
Purchase #5	$21.79	4.427%	$22.7546	$22.75	$22.75	$22.80
Purchase #6	$186.48	5.312%	$196.3858	$196.39	$196.40	$196.40
Purchase #7	$94.84	10.199%	$104.5127	$104.51	$104.50	$104.50
7 purchase totals =	$1,041.81		$1,127.9758	$1,127.97	$1,128.00	$1,128.00