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	$239.77	10.651%	$265.3079	$265.31	$265.30	$265.30
Purchase #2	$106.40	11.424%	$118.5551	$118.56	$118.55	$118.60
Purchase #3	$19.54	10.533%	$21.5981	$21.60	$21.60	$21.60
Purchase #4	$164.25	6.682%	$175.2252	$175.23	$175.25	$175.20
Purchase #5	$115.50	10.769%	$127.9382	$127.94	$127.95	$127.90
Purchase #6	$239.28	5.754%	$253.0482	$253.05	$253.05	$253.00
Purchase #7	$62.59	11.503%	$69.7897	$69.79	$69.80	$69.80
7 purchase totals =	$947.33		$1,031.4624	$1,031.48	$1,031.50	$1,031.40