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	$39.51	12.773%	$44.5566	$44.56	$44.55	$44.60
Purchase #2	$105.42	7.504%	$113.3307	$113.33	$113.35	$113.30
Purchase #3	$106.62	7.252%	$114.3521	$114.35	$114.35	$114.40
Purchase #4	$25.58	6.752%	$27.3072	$27.31	$27.30	$27.30
Purchase #5	$114.29	11.609%	$127.5579	$127.56	$127.55	$127.60
Purchase #6	$48.37	12.126%	$54.2353	$54.24	$54.25	$54.20
Purchase #7	$209.56	9.243%	$228.9296	$228.93	$228.95	$228.90
7 purchase totals =	$649.35		$710.2694	$710.28	$710.30	$710.30