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	$200.89	4.586%	$210.1028	$210.10	$210.10	$210.10
Purchase #2	$183.39	7.171%	$196.5409	$196.54	$196.55	$196.50
Purchase #3	$125.35	13.408%	$142.1569	$142.16	$142.15	$142.20
Purchase #4	$136.40	7.667%	$146.8578	$146.86	$146.85	$146.90
Purchase #5	$177.53	4.380%	$185.3058	$185.31	$185.30	$185.30
Purchase #6	$68.96	3.402%	$71.306	$71.31	$71.30	$71.30
Purchase #7	$164.53	8.307%	$178.1975	$178.20	$178.20	$178.20
7 purchase totals =	$1,057.05		$1,130.4677	$1,130.48	$1,130.45	$1,130.50