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	$120.76	6.158%	$128.1964	$128.20	$128.20	$128.20
Purchase #2	$57.69	4.521%	$60.2982	$60.30	$60.30	$60.30
Purchase #3	$198.94	3.419%	$205.7418	$205.74	$205.75	$205.70
Purchase #4	$209.92	7.610%	$225.8949	$225.89	$225.90	$225.90
Purchase #5	$72.89	13.382%	$82.6441	$82.64	$82.65	$82.60
Purchase #6	$196.26	9.752%	$215.3993	$215.40	$215.40	$215.40
Purchase #7	$249.40	5.382%	$262.8227	$262.82	$262.80	$262.80
7 purchase totals =	$1,105.86		$1,180.9974	$1,180.99	$1,181.00	$1,180.90