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	$41.73	4.437%	$43.5816	$43.58	$43.60	$43.60
Purchase #2	$27.60	7.203%	$29.588	$29.59	$29.60	$29.60
Purchase #3	$188.31	12.632%	$212.0973	$212.10	$212.10	$212.10
Purchase #4	$183.94	6.814%	$196.4737	$196.47	$196.45	$196.50
Purchase #5	$182.37	3.370%	$188.5159	$188.52	$188.50	$188.50
Purchase #6	$70.89	3.795%	$73.5803	$73.58	$73.60	$73.60
Purchase #7	$165.48	8.117%	$178.912	$178.91	$178.90	$178.90
7 purchase totals =	$860.32		$922.7488	$922.75	$922.75	$922.80