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	$56.54	9.372%	$61.8389	$61.84	$61.85	$61.80
Purchase #2	$248.89	13.466%	$282.4055	$282.41	$282.40	$282.40
Purchase #3	$37.45	6.128%	$39.7449	$39.74	$39.75	$39.70
Purchase #4	$67.37	6.569%	$71.7955	$71.80	$71.80	$71.80
Purchase #5	$103.46	3.288%	$106.8618	$106.86	$106.85	$106.90
Purchase #6	$126.64	12.516%	$142.4903	$142.49	$142.50	$142.50
Purchase #7	$189.43	3.315%	$195.7096	$195.71	$195.70	$195.70
7 purchase totals =	$829.78		$900.8465	$900.85	$900.85	$900.80