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	$128.63	13.845%	$146.4388	$146.44	$146.45	$146.40
Purchase #2	$154.59	5.145%	$162.5437	$162.54	$162.55	$162.50
Purchase #3	$92.41	4.351%	$96.4308	$96.43	$96.45	$96.40
Purchase #4	$212.82	3.121%	$219.4621	$219.46	$219.45	$219.50
Purchase #5	$55.66	8.487%	$60.3839	$60.38	$60.40	$60.40
Purchase #6	$234.62	6.758%	$250.4756	$250.48	$250.50	$250.50
Purchase #7	$128.40	11.774%	$143.5178	$143.52	$143.50	$143.50
7 purchase totals =	$1,007.13		$1,079.2527	$1,079.25	$1,079.30	$1,079.20