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	$182.82	11.120%	$203.1496	$203.15	$203.15	$203.10
Purchase #2	$123.60	9.148%	$134.9069	$134.91	$134.90	$134.90
Purchase #3	$227.69	12.406%	$255.9372	$255.94	$255.95	$255.90
Purchase #4	$162.63	10.106%	$179.0654	$179.07	$179.05	$179.10
Purchase #5	$82.94	7.835%	$89.4383	$89.44	$89.45	$89.40
Purchase #6	$181.37	12.574%	$204.1755	$204.18	$204.20	$204.20
Purchase #7	$210.69	11.318%	$234.5359	$234.54	$234.55	$234.50
7 purchase totals =	$1,171.74		$1,301.2088	$1,301.23	$1,301.25	$1,301.10