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	$64.54	9.351%	$70.5751	$70.58	$70.60	$70.60
Purchase #2	$180.37	5.408%	$190.1244	$190.12	$190.10	$190.10
Purchase #3	$176.40	3.531%	$182.6287	$182.63	$182.65	$182.60
Purchase #4	$72.93	7.503%	$78.4019	$78.40	$78.40	$78.40
Purchase #5	$50.83	13.411%	$57.6468	$57.65	$57.65	$57.60
Purchase #6	$75.98	8.831%	$82.6898	$82.69	$82.70	$82.70
Purchase #7	$171.70	8.241%	$185.8498	$185.85	$185.85	$185.80
7 purchase totals =	$792.75		$847.9165	$847.92	$847.95	$847.80