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	$84.79	13.800%	$96.491	$96.49	$96.50	$96.50
Purchase #2	$164.74	8.641%	$178.9752	$178.98	$179.00	$179.00
Purchase #3	$165.94	10.557%	$183.4583	$183.46	$183.45	$183.50
Purchase #4	$115.62	7.496%	$124.2869	$124.29	$124.30	$124.30
Purchase #5	$139.75	4.772%	$146.4189	$146.42	$146.40	$146.40
Purchase #6	$51.96	13.667%	$59.0614	$59.06	$59.05	$59.10
Purchase #7	$224.33	4.202%	$233.7563	$233.76	$233.75	$233.80
7 purchase totals =	$947.13		$1,022.4480	$1,022.46	$1,022.45	$1,022.60