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	$188.92	11.261%	$210.1943	$210.19	$210.20	$210.20
Purchase #2	$114.37	11.474%	$127.4928	$127.49	$127.50	$127.50
Purchase #3	$135.63	7.683%	$146.0505	$146.05	$146.05	$146.10
Purchase #4	$132.25	5.123%	$139.0252	$139.03	$139.05	$139.00
Purchase #5	$211.55	7.623%	$227.6765	$227.68	$227.70	$227.70
Purchase #6	$70.28	8.863%	$76.5089	$76.51	$76.50	$76.50
Purchase #7	$157.90	6.632%	$168.3719	$168.37	$168.35	$168.40
7 purchase totals =	$1,010.90		$1,095.3201	$1,095.32	$1,095.35	$1,095.40