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	$159.61	9.679%	$175.0587	$175.06	$175.05	$175.10
Purchase #2	$27.82	12.525%	$31.3045	$31.30	$31.30	$31.30
Purchase #3	$90.91	11.548%	$101.4083	$101.41	$101.40	$101.40
Purchase #4	$127.49	13.635%	$144.8733	$144.87	$144.85	$144.90
Purchase #5	$115.37	7.754%	$124.3158	$124.32	$124.30	$124.30
Purchase #6	$228.79	13.449%	$259.56	$259.56	$259.55	$259.60
Purchase #7	$220.33	9.872%	$242.081	$242.08	$242.10	$242.10
7 purchase totals =	$970.32		$1,078.6016	$1,078.60	$1,078.55	$1,078.70