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	$90.88	12.287%	$102.0464	$102.05	$102.05	$102.00
Purchase #2	$246.59	11.109%	$273.9837	$273.98	$274.00	$274.00
Purchase #3	$213.59	7.527%	$229.6669	$229.67	$229.65	$229.70
Purchase #4	$133.33	6.603%	$142.1338	$142.13	$142.15	$142.10
Purchase #5	$175.34	3.484%	$181.4488	$181.45	$181.45	$181.40
Purchase #6	$137.45	13.367%	$155.8229	$155.82	$155.80	$155.80
Purchase #7	$77.88	3.742%	$80.7943	$80.79	$80.80	$80.80
7 purchase totals =	$1,075.06		$1,165.8968	$1,165.89	$1,165.90	$1,165.80