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	$85.90	4.636%	$89.8823	$89.88	$89.90	$89.90
Purchase #2	$67.92	5.283%	$71.5082	$71.51	$71.50	$71.50
Purchase #3	$123.94	12.293%	$139.1759	$139.18	$139.20	$139.20
Purchase #4	$146.75	3.835%	$152.3779	$152.38	$152.40	$152.40
Purchase #5	$209.91	4.557%	$219.4756	$219.48	$219.50	$219.50
Purchase #6	$154.64	6.333%	$164.4334	$164.43	$164.45	$164.40
Purchase #7	$210.87	6.749%	$225.1016	$225.10	$225.10	$225.10
7 purchase totals =	$999.93		$1,061.9549	$1,061.96	$1,062.05	$1,062.00