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	$19.57	6.263%	$20.7957	$20.80	$20.80	$20.80
Purchase #2	$65.58	13.296%	$74.2995	$74.30	$74.30	$74.30
Purchase #3	$184.86	6.307%	$196.5191	$196.52	$196.50	$196.50
Purchase #4	$77.94	7.292%	$83.6234	$83.62	$83.60	$83.60
Purchase #5	$235.84	5.365%	$248.4928	$248.49	$248.50	$248.50
Purchase #6	$224.42	4.859%	$235.3246	$235.32	$235.30	$235.30
Purchase #7	$153.51	12.780%	$173.1286	$173.13	$173.15	$173.10
7 purchase totals =	$961.72		$1,032.1837	$1,032.18	$1,032.15	$1,032.10