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	$191.45	12.681%	$215.7278	$215.73	$215.75	$215.70
Purchase #2	$84.94	13.272%	$96.2132	$96.21	$96.20	$96.20
Purchase #3	$52.85	5.193%	$55.5945	$55.59	$55.60	$55.60
Purchase #4	$5.30	3.317%	$5.4758	$5.48	$5.50	$5.50
Purchase #5	$57.44	6.565%	$61.2109	$61.21	$61.20	$61.20
Purchase #6	$151.77	8.533%	$164.7205	$164.72	$164.70	$164.70
Purchase #7	$90.49	9.287%	$98.8938	$98.89	$98.90	$98.90
7 purchase totals =	$634.24		$697.8365	$697.83	$697.85	$697.80