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	$240.86	11.579%	$268.7492	$268.75	$268.75	$268.70
Purchase #2	$42.41	13.139%	$47.9822	$47.98	$48.00	$48.00
Purchase #3	$86.78	13.634%	$98.6116	$98.61	$98.60	$98.60
Purchase #4	$104.32	11.809%	$116.6391	$116.64	$116.65	$116.60
Purchase #5	$188.61	12.144%	$211.5148	$211.51	$211.50	$211.50
Purchase #6	$228.52	7.707%	$246.132	$246.13	$246.15	$246.10
Purchase #7	$27.45	6.535%	$29.2439	$29.24	$29.25	$29.20
7 purchase totals =	$918.95		$1,018.8728	$1,018.86	$1,018.90	$1,018.70