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	$181.27	12.421%	$203.7855	$203.79	$203.80	$203.80
Purchase #2	$53.57	10.835%	$59.3743	$59.37	$59.35	$59.40
Purchase #3	$212.58	3.667%	$220.3753	$220.38	$220.40	$220.40
Purchase #4	$152.28	11.271%	$169.4435	$169.44	$169.45	$169.40
Purchase #5	$193.52	10.137%	$213.1371	$213.14	$213.15	$213.10
Purchase #6	$110.87	11.369%	$123.4748	$123.47	$123.45	$123.50
Purchase #7	$183.93	12.645%	$207.1879	$207.19	$207.20	$207.20
7 purchase totals =	$1,088.02		$1,196.7784	$1,196.78	$1,196.80	$1,196.80