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	$200.52	5.458%	$211.4644	$211.46	$211.45	$211.50
Purchase #2	$35.66	6.364%	$37.9294	$37.93	$37.95	$37.90
Purchase #3	$188.72	6.125%	$200.2791	$200.28	$200.30	$200.30
Purchase #4	$244.96	12.527%	$275.6461	$275.65	$275.65	$275.60
Purchase #5	$229.36	5.265%	$241.4358	$241.44	$241.45	$241.40
Purchase #6	$237.54	4.538%	$248.3196	$248.32	$248.30	$248.30
Purchase #7	$152.38	12.227%	$171.0115	$171.01	$171.00	$171.00
7 purchase totals =	$1,289.14		$1,386.0859	$1,386.09	$1,386.10	$1,386.00