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	$38.36	7.712%	$41.3183	$41.32	$41.30	$41.30
Purchase #2	$246.25	6.523%	$262.3129	$262.31	$262.30	$262.30
Purchase #3	$13.32	12.142%	$14.9373	$14.94	$14.95	$14.90
Purchase #4	$74.46	5.812%	$78.7876	$78.79	$78.80	$78.80
Purchase #5	$173.81	4.164%	$181.0474	$181.05	$181.05	$181.00
Purchase #6	$83.41	7.751%	$89.8751	$89.88	$89.90	$89.90
Purchase #7	$72.62	6.725%	$77.5037	$77.50	$77.50	$77.50
7 purchase totals =	$702.23		$745.7823	$745.79	$745.80	$745.70