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	$161.90	12.696%	$182.4548	$182.45	$182.45	$182.50
Purchase #2	$73.33	6.767%	$78.2922	$78.29	$78.30	$78.30
Purchase #3	$80.44	13.484%	$91.2865	$91.29	$91.30	$91.30
Purchase #4	$234.79	10.865%	$260.2999	$260.30	$260.30	$260.30
Purchase #5	$247.77	4.460%	$258.8205	$258.82	$258.80	$258.80
Purchase #6	$224.67	4.825%	$235.5103	$235.51	$235.50	$235.50
Purchase #7	$152.90	7.437%	$164.2712	$164.27	$164.25	$164.30
7 purchase totals =	$1,175.80		$1,270.9354	$1,270.93	$1,270.90	$1,271.00