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	$194.32	7.548%	$208.9873	$208.99	$209.00	$209.00
Purchase #2	$89.73	4.661%	$93.9123	$93.91	$93.90	$93.90
Purchase #3	$154.47	13.123%	$174.7411	$174.74	$174.75	$174.70
Purchase #4	$103.55	7.825%	$111.6528	$111.65	$111.65	$111.70
Purchase #5	$59.96	3.253%	$61.9105	$61.91	$61.90	$61.90
Purchase #6	$228.61	3.835%	$237.3772	$237.38	$237.40	$237.40
Purchase #7	$61.74	5.127%	$64.9054	$64.91	$64.90	$64.90
7 purchase totals =	$892.38		$953.4866	$953.49	$953.50	$953.50