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	$63.85	11.274%	$71.0484	$71.05	$71.05	$71.00
Purchase #2	$187.32	13.643%	$212.8761	$212.88	$212.90	$212.90
Purchase #3	$188.66	5.559%	$199.1476	$199.15	$199.15	$199.10
Purchase #4	$139.81	9.108%	$152.5439	$152.54	$152.55	$152.50
Purchase #5	$137.75	13.384%	$156.1865	$156.19	$156.20	$156.20
Purchase #6	$154.32	9.374%	$168.786	$168.79	$168.80	$168.80
Purchase #7	$131.54	7.770%	$141.7607	$141.76	$141.75	$141.80
7 purchase totals =	$1,003.25		$1,102.3492	$1,102.36	$1,102.40	$1,102.30