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	$146.41	4.187%	$152.5402	$152.54	$152.55	$152.50
Purchase #2	$243.86	8.711%	$265.1026	$265.10	$265.10	$265.10
Purchase #3	$141.71	6.553%	$150.9963	$151.00	$151.00	$151.00
Purchase #4	$137.37	3.716%	$142.4747	$142.47	$142.45	$142.50
Purchase #5	$180.65	4.245%	$188.3186	$188.32	$188.30	$188.30
Purchase #6	$86.59	8.800%	$94.2099	$94.21	$94.20	$94.20
Purchase #7	$97.77	3.236%	$100.9338	$100.93	$100.95	$100.90
7 purchase totals =	$1,034.36		$1,094.5761	$1,094.57	$1,094.55	$1,094.50