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	$249.39	5.198%	$262.3533	$262.35	$262.35	$262.40
Purchase #2	$62.30	4.777%	$65.2761	$65.28	$65.30	$65.30
Purchase #3	$73.70	6.461%	$78.4618	$78.46	$78.45	$78.50
Purchase #4	$19.56	6.556%	$20.8424	$20.84	$20.85	$20.80
Purchase #5	$159.56	11.780%	$178.3562	$178.36	$178.35	$178.40
Purchase #6	$62.29	13.255%	$70.5465	$70.55	$70.55	$70.50
Purchase #7	$135.81	4.855%	$142.4036	$142.40	$142.40	$142.40
7 purchase totals =	$762.61		$818.2399	$818.24	$818.25	$818.30