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	$178.79	9.754%	$196.2292	$196.23	$196.25	$196.20
Purchase #2	$109.69	7.257%	$117.6502	$117.65	$117.65	$117.70
Purchase #3	$187.56	9.549%	$205.4701	$205.47	$205.45	$205.50
Purchase #4	$61.86	8.129%	$66.8886	$66.89	$66.90	$66.90
Purchase #5	$228.80	8.288%	$247.7629	$247.76	$247.75	$247.80
Purchase #6	$98.64	13.652%	$112.1063	$112.11	$112.10	$112.10
Purchase #7	$116.31	6.724%	$124.1307	$124.13	$124.15	$124.10
7 purchase totals =	$981.65		$1,070.2380	$1,070.24	$1,070.25	$1,070.30