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	$221.93	11.670%	$247.8292	$247.83	$247.85	$247.80
Purchase #2	$56.28	3.321%	$58.1491	$58.15	$58.15	$58.10
Purchase #3	$79.47	3.208%	$82.0194	$82.02	$82.00	$82.00
Purchase #4	$226.55	6.161%	$240.5077	$240.51	$240.50	$240.50
Purchase #5	$18.32	8.518%	$19.8805	$19.88	$19.90	$19.90
Purchase #6	$211.85	5.117%	$222.6904	$222.69	$222.70	$222.70
Purchase #7	$166.27	13.264%	$188.3241	$188.32	$188.30	$188.30
7 purchase totals =	$980.67		$1,059.4004	$1,059.40	$1,059.40	$1,059.30