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	$95.37	10.665%	$105.5412	$105.54	$105.55	$105.50
Purchase #2	$183.44	9.207%	$200.3293	$200.33	$200.35	$200.30
Purchase #3	$226.91	5.300%	$238.9362	$238.94	$238.95	$238.90
Purchase #4	$70.33	5.441%	$74.1567	$74.16	$74.15	$74.20
Purchase #5	$76.39	3.687%	$79.2065	$79.21	$79.20	$79.20
Purchase #6	$189.51	11.795%	$211.8627	$211.86	$211.85	$211.90
Purchase #7	$120.52	9.846%	$132.3864	$132.39	$132.40	$132.40
7 purchase totals =	$962.47		$1,042.4190	$1,042.43	$1,042.45	$1,042.40