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	$77.91	9.480%	$85.2959	$85.30	$85.30	$85.30
Purchase #2	$172.79	10.633%	$191.1628	$191.16	$191.15	$191.20
Purchase #3	$171.93	7.411%	$184.6717	$184.67	$184.65	$184.70
Purchase #4	$234.80	10.204%	$258.759	$258.76	$258.75	$258.80
Purchase #5	$84.36	11.575%	$94.1247	$94.12	$94.10	$94.10
Purchase #6	$131.66	9.389%	$144.0216	$144.02	$144.00	$144.00
Purchase #7	$90.73	11.152%	$100.8482	$100.85	$100.85	$100.80
7 purchase totals =	$964.18		$1,058.8839	$1,058.88	$1,058.80	$1,058.90