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	$243.44	10.346%	$268.6263	$268.63	$268.65	$268.60
Purchase #2	$125.80	4.790%	$131.8258	$131.83	$131.85	$131.80
Purchase #3	$7.86	9.326%	$8.593	$8.59	$8.60	$8.60
Purchase #4	$55.84	6.245%	$59.3272	$59.33	$59.35	$59.30
Purchase #5	$13.83	4.470%	$14.4482	$14.45	$14.45	$14.40
Purchase #6	$85.35	5.292%	$89.8667	$89.87	$89.85	$89.90
Purchase #7	$192.63	6.156%	$204.4883	$204.49	$204.50	$204.50
7 purchase totals =	$724.75		$777.1755	$777.19	$777.25	$777.10