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	$148.77	13.797%	$169.2958	$169.30	$169.30	$169.30
Purchase #2	$197.81	6.753%	$211.1681	$211.17	$211.15	$211.20
Purchase #3	$161.70	12.523%	$181.9497	$181.95	$181.95	$181.90
Purchase #4	$33.84	6.770%	$36.131	$36.13	$36.15	$36.10
Purchase #5	$73.89	6.777%	$78.8975	$78.90	$78.90	$78.90
Purchase #6	$196.54	13.430%	$222.9353	$222.94	$222.95	$222.90
Purchase #7	$168.98	9.566%	$185.1446	$185.14	$185.15	$185.10
7 purchase totals =	$981.53		$1,085.5220	$1,085.53	$1,085.55	$1,085.40