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	$180.43	13.826%	$205.3763	$205.38	$205.40	$205.40
Purchase #2	$235.86	8.463%	$255.8208	$255.82	$255.80	$255.80
Purchase #3	$61.57	9.470%	$67.4007	$67.40	$67.40	$67.40
Purchase #4	$91.47	5.428%	$96.435	$96.44	$96.45	$96.40
Purchase #5	$26.86	3.342%	$27.7577	$27.76	$27.75	$27.80
Purchase #6	$183.69	5.660%	$194.0869	$194.09	$194.10	$194.10
Purchase #7	$231.36	8.705%	$251.4999	$251.50	$251.50	$251.50
7 purchase totals =	$1,011.24		$1,098.3773	$1,098.39	$1,098.40	$1,098.40