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	$114.52	3.258%	$118.2511	$118.25	$118.25	$118.30
Purchase #2	$156.58	8.825%	$170.3982	$170.40	$170.40	$170.40
Purchase #3	$114.68	12.345%	$128.8372	$128.84	$128.85	$128.80
Purchase #4	$140.27	5.857%	$148.4856	$148.49	$148.50	$148.50
Purchase #5	$100.44	5.412%	$105.8758	$105.88	$105.90	$105.90
Purchase #6	$158.34	11.373%	$176.348	$176.35	$176.35	$176.30
Purchase #7	$142.30	8.488%	$154.3784	$154.38	$154.40	$154.40
7 purchase totals =	$927.13		$1,002.5743	$1,002.59	$1,002.65	$1,002.60