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	$30.93	7.161%	$33.1449	$33.14	$33.15	$33.10
Purchase #2	$186.90	5.271%	$196.7515	$196.75	$196.75	$196.80
Purchase #3	$152.95	12.807%	$172.5383	$172.54	$172.55	$172.50
Purchase #4	$215.73	11.556%	$240.6598	$240.66	$240.65	$240.70
Purchase #5	$49.31	9.700%	$54.0931	$54.09	$54.10	$54.10
Purchase #6	$205.90	11.837%	$230.2724	$230.27	$230.25	$230.30
Purchase #7	$90.42	10.217%	$99.6582	$99.66	$99.65	$99.70
7 purchase totals =	$932.14		$1,027.1182	$1,027.11	$1,027.10	$1,027.20