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	$161.80	4.287%	$168.7364	$168.74	$168.75	$168.70
Purchase #2	$18.52	5.115%	$19.4673	$19.47	$19.45	$19.50
Purchase #3	$145.88	12.800%	$164.5526	$164.55	$164.55	$164.60
Purchase #4	$188.83	8.676%	$205.2129	$205.21	$205.20	$205.20
Purchase #5	$127.34	11.838%	$142.4145	$142.41	$142.40	$142.40
Purchase #6	$155.60	9.754%	$170.7772	$170.78	$170.80	$170.80
Purchase #7	$191.63	9.150%	$209.1641	$209.16	$209.15	$209.20
7 purchase totals =	$989.60		$1,080.3250	$1,080.32	$1,080.30	$1,080.40