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	$116.27	12.865%	$131.2281	$131.23	$131.25	$131.20
Purchase #2	$201.87	7.250%	$216.5056	$216.51	$216.50	$216.50
Purchase #3	$250.95	5.269%	$264.1726	$264.17	$264.15	$264.20
Purchase #4	$53.42	5.285%	$56.2432	$56.24	$56.25	$56.20
Purchase #5	$90.43	5.625%	$95.5167	$95.52	$95.50	$95.50
Purchase #6	$185.98	6.734%	$198.5039	$198.50	$198.50	$198.50
Purchase #7	$71.78	12.817%	$80.98	$80.98	$81.00	$81.00
7 purchase totals =	$970.70		$1,043.1501	$1,043.15	$1,043.15	$1,043.10