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	$184.54	6.501%	$196.5369	$196.54	$196.55	$196.50
Purchase #2	$121.85	5.753%	$128.86	$128.86	$128.85	$128.90
Purchase #3	$190.36	3.436%	$196.9008	$196.90	$196.90	$196.90
Purchase #4	$105.66	8.169%	$114.2914	$114.29	$114.30	$114.30
Purchase #5	$64.92	10.110%	$71.4834	$71.48	$71.50	$71.50
Purchase #6	$114.93	12.298%	$129.0641	$129.06	$129.05	$129.10
Purchase #7	$228.78	13.155%	$258.876	$258.88	$258.90	$258.90
7 purchase totals =	$1,011.04		$1,096.0126	$1,096.01	$1,096.05	$1,096.10