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	$168.45	6.222%	$178.931	$178.93	$178.95	$178.90
Purchase #2	$44.28	3.267%	$45.7266	$45.73	$45.75	$45.70
Purchase #3	$17.34	8.592%	$18.8299	$18.83	$18.85	$18.80
Purchase #4	$70.87	13.831%	$80.672	$80.67	$80.65	$80.70
Purchase #5	$212.63	5.293%	$223.8845	$223.88	$223.90	$223.90
Purchase #6	$98.51	13.222%	$111.535	$111.54	$111.55	$111.50
Purchase #7	$185.84	5.850%	$196.7116	$196.71	$196.70	$196.70
7 purchase totals =	$797.92		$856.2906	$856.29	$856.35	$856.20