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	$242.80	13.694%	$276.049	$276.05	$276.05	$276.00
Purchase #2	$219.92	5.111%	$231.1601	$231.16	$231.15	$231.20
Purchase #3	$65.92	9.133%	$71.9405	$71.94	$71.95	$71.90
Purchase #4	$83.58	3.535%	$86.5346	$86.53	$86.55	$86.50
Purchase #5	$69.40	3.825%	$72.0546	$72.05	$72.05	$72.10
Purchase #6	$195.85	9.487%	$214.4303	$214.43	$214.45	$214.40
Purchase #7	$162.91	7.716%	$175.4801	$175.48	$175.50	$175.50
7 purchase totals =	$1,040.38		$1,127.6492	$1,127.64	$1,127.70	$1,127.60