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	$82.89	8.501%	$89.9365	$89.94	$89.95	$89.90
Purchase #2	$144.42	4.622%	$151.0951	$151.10	$151.10	$151.10
Purchase #3	$122.96	5.587%	$129.8298	$129.83	$129.85	$129.80
Purchase #4	$147.97	11.561%	$165.0768	$165.08	$165.10	$165.10
Purchase #5	$215.61	11.751%	$240.9463	$240.95	$240.95	$240.90
Purchase #6	$123.44	8.765%	$134.2595	$134.26	$134.25	$134.30
Purchase #7	$140.36	5.789%	$148.4854	$148.49	$148.50	$148.50
7 purchase totals =	$977.65		$1,059.6294	$1,059.65	$1,059.70	$1,059.60