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	$126.84	3.607%	$131.4151	$131.42	$131.40	$131.40
Purchase #2	$200.69	13.596%	$227.9758	$227.98	$228.00	$228.00
Purchase #3	$100.37	9.153%	$109.5569	$109.56	$109.55	$109.60
Purchase #4	$92.85	13.764%	$105.6299	$105.63	$105.65	$105.60
Purchase #5	$169.70	10.502%	$187.5219	$187.52	$187.50	$187.50
Purchase #6	$111.84	7.341%	$120.0502	$120.05	$120.05	$120.10
Purchase #7	$217.72	4.772%	$228.1096	$228.11	$228.10	$228.10
7 purchase totals =	$1,020.01		$1,110.2594	$1,110.27	$1,110.25	$1,110.30