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	$104.44	4.863%	$109.5189	$109.52	$109.50	$109.50
Purchase #2	$83.42	3.320%	$86.1895	$86.19	$86.20	$86.20
Purchase #3	$18.75	9.729%	$20.5742	$20.57	$20.55	$20.60
Purchase #4	$54.99	7.378%	$59.0472	$59.05	$59.05	$59.00
Purchase #5	$50.56	7.229%	$54.215	$54.22	$54.20	$54.20
Purchase #6	$99.31	10.745%	$109.9809	$109.98	$110.00	$110.00
Purchase #7	$11.96	7.296%	$12.8326	$12.83	$12.85	$12.80
7 purchase totals =	$423.43		$452.3583	$452.36	$452.35	$452.30