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	$76.55	13.242%	$86.6868	$86.69	$86.70	$86.70
Purchase #2	$98.63	4.495%	$103.0634	$103.06	$103.05	$103.10
Purchase #3	$29.83	11.410%	$33.2336	$33.23	$33.25	$33.20
Purchase #4	$184.94	10.789%	$204.8932	$204.89	$204.90	$204.90
Purchase #5	$65.82	9.588%	$72.1308	$72.13	$72.15	$72.10
Purchase #6	$167.37	12.166%	$187.7322	$187.73	$187.75	$187.70
Purchase #7	$169.25	6.609%	$180.4357	$180.44	$180.45	$180.40
7 purchase totals =	$792.39		$868.1757	$868.17	$868.25	$868.10