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	$193.29	10.487%	$213.5603	$213.56	$213.55	$213.60
Purchase #2	$201.31	10.508%	$222.4637	$222.46	$222.45	$222.50
Purchase #3	$134.47	5.607%	$142.0097	$142.01	$142.00	$142.00
Purchase #4	$24.79	13.527%	$28.1433	$28.14	$28.15	$28.10
Purchase #5	$168.67	4.627%	$176.4744	$176.47	$176.45	$176.50
Purchase #6	$223.43	10.254%	$246.3405	$246.34	$246.35	$246.30
Purchase #7	$224.79	11.385%	$250.3823	$250.38	$250.40	$250.40
7 purchase totals =	$1,170.75		$1,279.3742	$1,279.36	$1,279.35	$1,279.40