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	$185.65	6.873%	$198.4097	$198.41	$198.40	$198.40
Purchase #2	$127.91	7.552%	$137.5698	$137.57	$137.55	$137.60
Purchase #3	$86.98	5.533%	$91.7926	$91.79	$91.80	$91.80
Purchase #4	$188.25	13.429%	$213.5301	$213.53	$213.55	$213.50
Purchase #5	$99.31	9.774%	$109.0166	$109.02	$109.00	$109.00
Purchase #6	$67.68	3.834%	$70.2749	$70.27	$70.25	$70.30
Purchase #7	$113.62	8.485%	$123.2607	$123.26	$123.25	$123.30
7 purchase totals =	$869.40		$943.8544	$943.85	$943.80	$943.90