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	$158.83	5.835%	$168.0977	$168.10	$168.10	$168.10
Purchase #2	$161.27	6.131%	$171.1575	$171.16	$171.15	$171.20
Purchase #3	$29.39	7.367%	$31.5552	$31.56	$31.55	$31.60
Purchase #4	$179.58	9.473%	$196.5916	$196.59	$196.60	$196.60
Purchase #5	$207.78	6.608%	$221.5101	$221.51	$221.50	$221.50
Purchase #6	$177.38	6.827%	$189.4897	$189.49	$189.50	$189.50
Purchase #7	$47.31	10.631%	$52.3395	$52.34	$52.35	$52.30
7 purchase totals =	$961.54		$1,030.7413	$1,030.75	$1,030.75	$1,030.80