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	$110.50	11.528%	$123.2384	$123.24	$123.25	$123.20
Purchase #2	$116.91	8.808%	$127.2074	$127.21	$127.20	$127.20
Purchase #3	$116.50	10.645%	$128.9014	$128.90	$128.90	$128.90
Purchase #4	$96.42	13.745%	$109.6729	$109.67	$109.65	$109.70
Purchase #5	$235.39	13.340%	$266.791	$266.79	$266.80	$266.80
Purchase #6	$215.82	12.501%	$242.7997	$242.80	$242.80	$242.80
Purchase #7	$56.34	9.440%	$61.6585	$61.66	$61.65	$61.70
7 purchase totals =	$947.88		$1,060.2693	$1,060.27	$1,060.25	$1,060.30