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	$233.41	7.475%	$250.8574	$250.86	$250.85	$250.90
Purchase #2	$240.86	10.755%	$266.7645	$266.76	$266.75	$266.80
Purchase #3	$122.46	3.731%	$127.029	$127.03	$127.05	$127.00
Purchase #4	$183.58	11.850%	$205.3342	$205.33	$205.35	$205.30
Purchase #5	$81.56	10.577%	$90.1866	$90.19	$90.20	$90.20
Purchase #6	$100.90	11.218%	$112.219	$112.22	$112.20	$112.20
Purchase #7	$200.84	7.326%	$215.5535	$215.55	$215.55	$215.60
7 purchase totals =	$1,163.61		$1,267.9442	$1,267.94	$1,267.95	$1,268.00