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	$175.98	3.414%	$181.988	$181.99	$182.00	$182.00
Purchase #2	$185.30	6.106%	$196.6144	$196.61	$196.60	$196.60
Purchase #3	$84.61	12.500%	$95.1863	$95.19	$95.20	$95.20
Purchase #4	$123.45	6.232%	$131.1434	$131.14	$131.15	$131.10
Purchase #5	$36.94	7.705%	$39.7862	$39.79	$39.80	$39.80
Purchase #6	$98.68	7.270%	$105.854	$105.85	$105.85	$105.90
Purchase #7	$250.30	12.329%	$281.1595	$281.16	$281.15	$281.20
7 purchase totals =	$955.26		$1,031.7318	$1,031.73	$1,031.75	$1,031.80