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	$176.61	6.135%	$187.445	$187.45	$187.45	$187.40
Purchase #2	$101.27	13.339%	$114.7784	$114.78	$114.80	$114.80
Purchase #3	$131.82	12.123%	$147.8005	$147.80	$147.80	$147.80
Purchase #4	$172.67	8.610%	$187.5369	$187.54	$187.55	$187.50
Purchase #5	$21.30	7.834%	$22.9686	$22.97	$22.95	$23.00
Purchase #6	$96.91	3.429%	$100.233	$100.23	$100.25	$100.20
Purchase #7	$99.68	11.703%	$111.3456	$111.35	$111.35	$111.30
7 purchase totals =	$800.26		$872.1080	$872.12	$872.15	$872.00