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	$150.85	12.345%	$169.4724	$169.47	$169.45	$169.50
Purchase #2	$42.66	6.551%	$45.4547	$45.45	$45.45	$45.50
Purchase #3	$29.39	7.392%	$31.5625	$31.56	$31.55	$31.60
Purchase #4	$203.44	5.731%	$215.0991	$215.10	$215.10	$215.10
Purchase #5	$241.55	11.236%	$268.6906	$268.69	$268.70	$268.70
Purchase #6	$182.37	7.763%	$196.5274	$196.53	$196.55	$196.50
Purchase #7	$165.52	3.344%	$171.055	$171.06	$171.05	$171.10
7 purchase totals =	$1,015.78		$1,097.8617	$1,097.86	$1,097.85	$1,098.00