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	$242.34	4.799%	$253.9699	$253.97	$253.95	$254.00
Purchase #2	$103.90	7.540%	$111.7341	$111.73	$111.75	$111.70
Purchase #3	$156.71	5.715%	$165.666	$165.67	$165.65	$165.70
Purchase #4	$230.50	3.334%	$238.1849	$238.18	$238.20	$238.20
Purchase #5	$97.87	4.487%	$102.2614	$102.26	$102.25	$102.30
Purchase #6	$171.54	6.814%	$183.2287	$183.23	$183.25	$183.20
Purchase #7	$181.70	8.182%	$196.5667	$196.57	$196.55	$196.60
7 purchase totals =	$1,184.56		$1,251.6117	$1,251.61	$1,251.60	$1,251.70