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	$238.57	11.176%	$265.2326	$265.23	$265.25	$265.20
Purchase #2	$95.56	3.336%	$98.7479	$98.75	$98.75	$98.70
Purchase #3	$203.59	10.561%	$225.0911	$225.09	$225.10	$225.10
Purchase #4	$155.68	4.404%	$162.5361	$162.54	$162.55	$162.50
Purchase #5	$41.45	3.423%	$42.8688	$42.87	$42.85	$42.90
Purchase #6	$135.59	13.692%	$154.155	$154.16	$154.15	$154.20
Purchase #7	$68.85	5.642%	$72.7345	$72.73	$72.75	$72.70
7 purchase totals =	$939.29		$1,021.3660	$1,021.37	$1,021.40	$1,021.30