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	$54.43	12.489%	$61.2278	$61.23	$61.25	$61.20
Purchase #2	$174.86	12.578%	$196.8539	$196.85	$196.85	$196.90
Purchase #3	$143.35	7.609%	$154.2575	$154.26	$154.25	$154.30
Purchase #4	$82.73	8.536%	$89.7918	$89.79	$89.80	$89.80
Purchase #5	$133.83	6.189%	$142.1127	$142.11	$142.10	$142.10
Purchase #6	$32.63	4.647%	$34.1463	$34.15	$34.15	$34.10
Purchase #7	$231.90	5.190%	$243.9356	$243.94	$243.95	$243.90
7 purchase totals =	$853.73		$922.3256	$922.33	$922.35	$922.30