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	$249.64	9.695%	$273.8426	$273.84	$273.85	$273.80
Purchase #2	$201.44	6.743%	$215.0231	$215.02	$215.00	$215.00
Purchase #3	$53.30	5.621%	$56.296	$56.30	$56.30	$56.30
Purchase #4	$131.56	6.277%	$139.818	$139.82	$139.80	$139.80
Purchase #5	$85.93	10.669%	$95.0979	$95.10	$95.10	$95.10
Purchase #6	$175.73	6.124%	$186.4917	$186.49	$186.50	$186.50
Purchase #7	$107.37	10.664%	$118.8199	$118.82	$118.80	$118.80
7 purchase totals =	$1,004.97		$1,085.3892	$1,085.39	$1,085.35	$1,085.30