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	$200.95	9.342%	$219.7227	$219.72	$219.70	$219.70
Purchase #2	$127.83	7.596%	$137.54	$137.54	$137.55	$137.50
Purchase #3	$11.74	3.745%	$12.1797	$12.18	$12.20	$12.20
Purchase #4	$174.57	9.574%	$191.2833	$191.28	$191.30	$191.30
Purchase #5	$147.67	11.364%	$164.4512	$164.45	$164.45	$164.50
Purchase #6	$243.59	10.206%	$268.4508	$268.45	$268.45	$268.50
Purchase #7	$95.40	4.508%	$99.7006	$99.70	$99.70	$99.70
7 purchase totals =	$1,001.75		$1,093.3283	$1,093.32	$1,093.35	$1,093.40