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	$180.30	13.601%	$204.8226	$204.82	$204.80	$204.80
Purchase #2	$71.52	9.275%	$78.1535	$78.15	$78.15	$78.20
Purchase #3	$132.62	7.623%	$142.7296	$142.73	$142.75	$142.70
Purchase #4	$242.27	3.737%	$251.3236	$251.32	$251.30	$251.30
Purchase #5	$90.27	7.236%	$96.8019	$96.80	$96.80	$96.80
Purchase #6	$150.95	4.296%	$157.4348	$157.43	$157.45	$157.40
Purchase #7	$96.70	4.779%	$101.3213	$101.32	$101.30	$101.30
7 purchase totals =	$964.63		$1,032.5873	$1,032.57	$1,032.55	$1,032.50