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	$108.53	5.543%	$114.5458	$114.55	$114.55	$114.50
Purchase #2	$82.33	4.138%	$85.7368	$85.74	$85.75	$85.70
Purchase #3	$124.47	6.143%	$132.1162	$132.12	$132.10	$132.10
Purchase #4	$43.86	9.853%	$48.1815	$48.18	$48.20	$48.20
Purchase #5	$191.30	12.773%	$215.7347	$215.73	$215.75	$215.70
Purchase #6	$223.92	11.257%	$249.1267	$249.13	$249.15	$249.10
Purchase #7	$216.88	10.670%	$240.0211	$240.02	$240.00	$240.00
7 purchase totals =	$991.29		$1,085.4628	$1,085.47	$1,085.50	$1,085.30