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	$137.83	4.712%	$144.3245	$144.32	$144.30	$144.30
Purchase #2	$61.94	7.193%	$66.3953	$66.40	$66.40	$66.40
Purchase #3	$154.70	3.676%	$160.3868	$160.39	$160.40	$160.40
Purchase #4	$206.56	4.516%	$215.8882	$215.89	$215.90	$215.90
Purchase #5	$85.52	13.336%	$96.9249	$96.92	$96.90	$96.90
Purchase #6	$103.44	7.614%	$111.3159	$111.32	$111.30	$111.30
Purchase #7	$198.69	11.332%	$221.2056	$221.21	$221.20	$221.20
7 purchase totals =	$948.68		$1,016.4412	$1,016.45	$1,016.40	$1,016.40