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	$219.48	11.568%	$244.8694	$244.87	$244.85	$244.90
Purchase #2	$22.63	12.764%	$25.5185	$25.52	$25.50	$25.50
Purchase #3	$174.91	12.260%	$196.354	$196.35	$196.35	$196.40
Purchase #4	$129.39	7.527%	$139.1292	$139.13	$139.15	$139.10
Purchase #5	$189.98	13.302%	$215.2511	$215.25	$215.25	$215.30
Purchase #6	$60.83	3.538%	$62.9822	$62.98	$63.00	$63.00
Purchase #7	$84.74	5.677%	$89.5507	$89.55	$89.55	$89.60
7 purchase totals =	$881.96		$973.6551	$973.65	$973.65	$973.80