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	$89.88	12.753%	$101.3424	$101.34	$101.35	$101.30
Purchase #2	$227.39	6.126%	$241.3199	$241.32	$241.30	$241.30
Purchase #3	$184.49	5.445%	$194.5355	$194.54	$194.55	$194.50
Purchase #4	$201.94	9.399%	$220.9203	$220.92	$220.90	$220.90
Purchase #5	$95.34	5.392%	$100.4807	$100.48	$100.50	$100.50
Purchase #6	$104.83	6.275%	$111.4081	$111.41	$111.40	$111.40
Purchase #7	$68.70	6.627%	$73.2527	$73.25	$73.25	$73.30
7 purchase totals =	$972.57		$1,043.2596	$1,043.26	$1,043.25	$1,043.20