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	$30.44	9.264%	$33.26	$33.26	$33.25	$33.30
Purchase #2	$169.46	4.128%	$176.4553	$176.46	$176.45	$176.50
Purchase #3	$148.41	13.631%	$168.6398	$168.64	$168.65	$168.60
Purchase #4	$169.75	3.196%	$175.1752	$175.18	$175.20	$175.20
Purchase #5	$200.72	7.400%	$215.5733	$215.57	$215.55	$215.60
Purchase #6	$50.86	10.813%	$56.3595	$56.36	$56.35	$56.40
Purchase #7	$211.52	4.784%	$221.6391	$221.64	$221.65	$221.60
7 purchase totals =	$981.16		$1,047.1022	$1,047.11	$1,047.10	$1,047.20