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	$169.85	6.552%	$180.9786	$180.98	$181.00	$181.00
Purchase #2	$228.82	6.512%	$243.7208	$243.72	$243.70	$243.70
Purchase #3	$7.67	3.358%	$7.9276	$7.93	$7.95	$7.90
Purchase #4	$235.33	4.155%	$245.108	$245.11	$245.10	$245.10
Purchase #5	$100.58	4.856%	$105.4642	$105.46	$105.45	$105.50
Purchase #6	$229.50	5.265%	$241.5832	$241.58	$241.60	$241.60
Purchase #7	$22.71	7.702%	$24.4591	$24.46	$24.45	$24.50
7 purchase totals =	$994.46		$1,049.2415	$1,049.24	$1,049.25	$1,049.30