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	$111.65	5.798%	$118.1235	$118.12	$118.10	$118.10
Purchase #2	$248.64	7.299%	$266.7882	$266.79	$266.80	$266.80
Purchase #3	$176.47	7.821%	$190.2717	$190.27	$190.25	$190.30
Purchase #4	$141.51	12.242%	$158.8337	$158.83	$158.85	$158.80
Purchase #5	$94.61	3.783%	$98.1891	$98.19	$98.20	$98.20
Purchase #6	$183.63	6.801%	$196.1187	$196.12	$196.10	$196.10
Purchase #7	$88.75	8.770%	$96.5334	$96.53	$96.55	$96.50
7 purchase totals =	$1,045.26		$1,124.8583	$1,124.85	$1,124.85	$1,124.80