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	$240.72	8.181%	$260.4133	$260.41	$260.40	$260.40
Purchase #2	$96.79	8.622%	$105.1352	$105.14	$105.15	$105.10
Purchase #3	$179.27	8.140%	$193.8626	$193.86	$193.85	$193.90
Purchase #4	$209.60	4.736%	$219.5267	$219.53	$219.55	$219.50
Purchase #5	$54.78	12.253%	$61.4922	$61.49	$61.50	$61.50
Purchase #6	$39.82	8.174%	$43.0749	$43.07	$43.05	$43.10
Purchase #7	$118.80	4.579%	$124.2399	$124.24	$124.25	$124.20
7 purchase totals =	$939.78		$1,007.7448	$1,007.74	$1,007.75	$1,007.70