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	$180.43	11.206%	$200.649	$200.65	$200.65	$200.60
Purchase #2	$170.40	12.568%	$191.8159	$191.82	$191.80	$191.80
Purchase #3	$247.26	10.764%	$273.8751	$273.88	$273.90	$273.90
Purchase #4	$19.38	8.261%	$20.981	$20.98	$21.00	$21.00
Purchase #5	$162.45	11.685%	$181.4323	$181.43	$181.45	$181.40
Purchase #6	$209.94	3.754%	$217.8211	$217.82	$217.80	$217.80
Purchase #7	$143.53	13.539%	$162.9625	$162.96	$162.95	$163.00
7 purchase totals =	$1,133.39		$1,249.5369	$1,249.54	$1,249.55	$1,249.50