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	$34.56	5.199%	$36.3568	$36.36	$36.35	$36.40
Purchase #2	$111.57	4.456%	$116.5416	$116.54	$116.55	$116.50
Purchase #3	$136.25	6.218%	$144.722	$144.72	$144.70	$144.70
Purchase #4	$180.45	8.756%	$196.2502	$196.25	$196.25	$196.30
Purchase #5	$89.65	9.669%	$98.3183	$98.32	$98.30	$98.30
Purchase #6	$178.59	12.793%	$201.437	$201.44	$201.45	$201.40
Purchase #7	$219.32	6.495%	$233.5648	$233.56	$233.55	$233.60
7 purchase totals =	$950.39		$1,027.1907	$1,027.19	$1,027.15	$1,027.20