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	$38.76	13.419%	$43.9612	$43.96	$43.95	$44.00
Purchase #2	$220.38	4.391%	$230.0569	$230.06	$230.05	$230.10
Purchase #3	$174.83	12.399%	$196.5072	$196.51	$196.50	$196.50
Purchase #4	$123.58	12.445%	$138.9595	$138.96	$138.95	$139.00
Purchase #5	$97.46	11.566%	$108.7322	$108.73	$108.75	$108.70
Purchase #6	$182.39	10.113%	$200.8351	$200.84	$200.85	$200.80
Purchase #7	$129.76	7.223%	$139.1326	$139.13	$139.15	$139.10
7 purchase totals =	$967.16		$1,058.1847	$1,058.19	$1,058.20	$1,058.20