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	$225.89	6.592%	$240.7807	$240.78	$240.80	$240.80
Purchase #2	$11.44	7.770%	$12.3289	$12.33	$12.35	$12.30
Purchase #3	$91.74	8.462%	$99.503	$99.50	$99.50	$99.50
Purchase #4	$187.95	4.685%	$196.7555	$196.76	$196.75	$196.80
Purchase #5	$208.29	12.659%	$234.6574	$234.66	$234.65	$234.70
Purchase #6	$159.58	4.212%	$166.3015	$166.30	$166.30	$166.30
Purchase #7	$57.53	4.409%	$60.0665	$60.07	$60.05	$60.10
7 purchase totals =	$942.42		$1,010.3935	$1,010.40	$1,010.40	$1,010.50