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	$96.89	4.817%	$101.5572	$101.56	$101.55	$101.60
Purchase #2	$80.60	11.817%	$90.1245	$90.12	$90.10	$90.10
Purchase #3	$107.85	12.834%	$121.6915	$121.69	$121.70	$121.70
Purchase #4	$176.89	6.794%	$188.9079	$188.91	$188.90	$188.90
Purchase #5	$98.56	13.601%	$111.9651	$111.97	$111.95	$112.00
Purchase #6	$128.28	3.209%	$132.3965	$132.40	$132.40	$132.40
Purchase #7	$131.91	6.280%	$140.1939	$140.19	$140.20	$140.20
7 purchase totals =	$820.98		$886.8366	$886.84	$886.80	$886.90