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	$85.47	13.217%	$96.7666	$96.77	$96.75	$96.80
Purchase #2	$86.50	4.804%	$90.6555	$90.66	$90.65	$90.70
Purchase #3	$183.70	8.210%	$198.7818	$198.78	$198.80	$198.80
Purchase #4	$172.48	13.793%	$196.2702	$196.27	$196.25	$196.30
Purchase #5	$220.40	5.171%	$231.7969	$231.80	$231.80	$231.80
Purchase #6	$219.58	13.187%	$248.536	$248.54	$248.55	$248.50
Purchase #7	$222.89	8.818%	$242.5444	$242.54	$242.55	$242.50
7 purchase totals =	$1,191.02		$1,305.3514	$1,305.36	$1,305.35	$1,305.40