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	$115.42	11.161%	$128.302	$128.30	$128.30	$128.30
Purchase #2	$182.78	10.149%	$201.3303	$201.33	$201.35	$201.30
Purchase #3	$110.82	3.339%	$114.5203	$114.52	$114.50	$114.50
Purchase #4	$204.82	13.137%	$231.7272	$231.73	$231.75	$231.70
Purchase #5	$123.59	3.362%	$127.7451	$127.75	$127.75	$127.70
Purchase #6	$56.97	4.766%	$59.6852	$59.69	$59.70	$59.70
Purchase #7	$149.98	11.165%	$166.7253	$166.73	$166.75	$166.70
7 purchase totals =	$944.38		$1,030.0354	$1,030.05	$1,030.10	$1,029.90