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	$179.76	3.410%	$185.8898	$185.89	$185.90	$185.90
Purchase #2	$240.31	7.104%	$257.3816	$257.38	$257.40	$257.40
Purchase #3	$161.97	7.741%	$174.5081	$174.51	$174.50	$174.50
Purchase #4	$199.91	13.255%	$226.4081	$226.41	$226.40	$226.40
Purchase #5	$105.73	10.143%	$116.4542	$116.45	$116.45	$116.50
Purchase #6	$64.56	9.568%	$70.7371	$70.74	$70.75	$70.70
Purchase #7	$25.83	9.453%	$28.2717	$28.27	$28.25	$28.30
7 purchase totals =	$978.07		$1,059.6506	$1,059.65	$1,059.65	$1,059.70