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	$245.43	8.388%	$266.0167	$266.02	$266.00	$266.00
Purchase #2	$39.44	4.700%	$41.2937	$41.29	$41.30	$41.30
Purchase #3	$114.55	4.614%	$119.8353	$119.84	$119.85	$119.80
Purchase #4	$174.91	9.745%	$191.955	$191.96	$191.95	$192.00
Purchase #5	$241.31	7.463%	$259.319	$259.32	$259.30	$259.30
Purchase #6	$74.36	11.319%	$82.7768	$82.78	$82.80	$82.80
Purchase #7	$143.40	6.209%	$152.3037	$152.30	$152.30	$152.30
7 purchase totals =	$1,033.40		$1,113.5002	$1,113.51	$1,113.50	$1,113.50