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	$185.98	5.462%	$196.1382	$196.14	$196.15	$196.10
Purchase #2	$69.77	12.423%	$78.4375	$78.44	$78.45	$78.40
Purchase #3	$233.86	10.308%	$257.9663	$257.97	$257.95	$258.00
Purchase #4	$191.92	9.302%	$209.7724	$209.77	$209.75	$209.80
Purchase #5	$130.96	6.835%	$139.9111	$139.91	$139.90	$139.90
Purchase #6	$92.69	13.571%	$105.269	$105.27	$105.25	$105.30
Purchase #7	$175.77	3.837%	$182.5143	$182.51	$182.50	$182.50
7 purchase totals =	$1,080.95		$1,170.0088	$1,170.01	$1,169.95	$1,170.00