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	$176.97	11.259%	$196.8951	$196.90	$196.90	$196.90
Purchase #2	$12.76	5.546%	$13.4677	$13.47	$13.45	$13.50
Purchase #3	$163.72	12.665%	$184.4551	$184.46	$184.45	$184.50
Purchase #4	$72.28	11.790%	$80.8018	$80.80	$80.80	$80.80
Purchase #5	$55.34	11.154%	$61.5126	$61.51	$61.50	$61.50
Purchase #6	$246.28	10.122%	$271.2085	$271.21	$271.20	$271.20
Purchase #7	$81.99	11.558%	$91.4664	$91.47	$91.45	$91.50
7 purchase totals =	$809.34		$899.8072	$899.82	$899.75	$899.90