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	$215.41	3.304%	$222.5271	$222.53	$222.55	$222.50
Purchase #2	$112.69	13.603%	$128.0192	$128.02	$128.00	$128.00
Purchase #3	$215.81	9.535%	$236.3875	$236.39	$236.40	$236.40
Purchase #4	$199.84	8.347%	$216.5206	$216.52	$216.50	$216.50
Purchase #5	$98.87	12.277%	$111.0083	$111.01	$111.00	$111.00
Purchase #6	$229.96	7.721%	$247.7152	$247.72	$247.70	$247.70
Purchase #7	$89.45	13.109%	$101.176	$101.18	$101.20	$101.20
7 purchase totals =	$1,162.03		$1,263.3539	$1,263.37	$1,263.35	$1,263.30