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	$108.36	9.869%	$119.054	$119.05	$119.05	$119.10
Purchase #2	$214.91	10.479%	$237.4304	$237.43	$237.45	$237.40
Purchase #3	$80.55	12.822%	$90.8781	$90.88	$90.90	$90.90
Purchase #4	$53.67	4.340%	$55.9993	$56.00	$56.00	$56.00
Purchase #5	$139.39	12.550%	$156.8834	$156.88	$156.90	$156.90
Purchase #6	$72.76	13.700%	$82.7281	$82.73	$82.75	$82.70
Purchase #7	$215.66	3.384%	$222.9579	$222.96	$222.95	$223.00
7 purchase totals =	$885.30		$965.9312	$965.93	$966.00	$966.00