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	$86.67	3.419%	$89.6332	$89.63	$89.65	$89.60
Purchase #2	$118.75	9.831%	$130.4243	$130.42	$130.40	$130.40
Purchase #3	$85.48	12.839%	$96.4548	$96.45	$96.45	$96.50
Purchase #4	$233.92	6.671%	$249.5248	$249.52	$249.50	$249.50
Purchase #5	$73.91	6.380%	$78.6255	$78.63	$78.65	$78.60
Purchase #6	$248.86	12.481%	$279.9202	$279.92	$279.90	$279.90
Purchase #7	$135.29	9.784%	$148.5268	$148.53	$148.55	$148.50
7 purchase totals =	$982.88		$1,073.1096	$1,073.10	$1,073.10	$1,073.00