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	$244.35	10.123%	$269.0856	$269.09	$269.10	$269.10
Purchase #2	$123.25	3.623%	$127.7153	$127.72	$127.70	$127.70
Purchase #3	$104.97	5.282%	$110.5145	$110.51	$110.50	$110.50
Purchase #4	$230.56	6.667%	$245.9314	$245.93	$245.95	$245.90
Purchase #5	$17.38	5.246%	$18.2918	$18.29	$18.30	$18.30
Purchase #6	$196.86	3.722%	$204.1871	$204.19	$204.20	$204.20
Purchase #7	$73.39	7.562%	$78.9398	$78.94	$78.95	$78.90
7 purchase totals =	$990.76		$1,054.6655	$1,054.67	$1,054.70	$1,054.60