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	$98.84	12.715%	$111.4075	$111.41	$111.40	$111.40
Purchase #2	$14.91	4.136%	$15.5267	$15.53	$15.55	$15.50
Purchase #3	$170.36	3.244%	$175.8865	$175.89	$175.90	$175.90
Purchase #4	$43.38	10.263%	$47.8321	$47.83	$47.85	$47.80
Purchase #5	$47.69	11.193%	$53.0279	$53.03	$53.05	$53.00
Purchase #6	$200.66	11.765%	$224.2676	$224.27	$224.25	$224.30
Purchase #7	$172.68	7.807%	$186.1611	$186.16	$186.15	$186.20
7 purchase totals =	$748.52		$814.1094	$814.12	$814.15	$814.10