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	$44.59	5.756%	$47.1566	$47.16	$47.15	$47.20
Purchase #2	$90.93	5.869%	$96.2667	$96.27	$96.25	$96.30
Purchase #3	$48.81	5.436%	$51.4633	$51.46	$51.45	$51.50
Purchase #4	$131.95	5.740%	$139.5239	$139.52	$139.50	$139.50
Purchase #5	$171.96	9.334%	$188.0107	$188.01	$188.00	$188.00
Purchase #6	$250.92	6.473%	$267.1621	$267.16	$267.15	$267.20
Purchase #7	$60.32	12.621%	$67.933	$67.93	$67.95	$67.90
7 purchase totals =	$799.48		$857.5163	$857.51	$857.45	$857.60