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	$179.60	11.726%	$200.6599	$200.66	$200.65	$200.70
Purchase #2	$161.59	10.349%	$178.3129	$178.31	$178.30	$178.30
Purchase #3	$135.52	7.395%	$145.5417	$145.54	$145.55	$145.50
Purchase #4	$128.61	12.308%	$144.4393	$144.44	$144.45	$144.40
Purchase #5	$49.88	10.384%	$55.0595	$55.06	$55.05	$55.10
Purchase #6	$150.33	12.125%	$168.5575	$168.56	$168.55	$168.60
Purchase #7	$65.71	7.149%	$70.4076	$70.41	$70.40	$70.40
7 purchase totals =	$871.24		$962.9784	$962.98	$962.95	$963.00