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	$114.79	11.360%	$127.8301	$127.83	$127.85	$127.80
Purchase #2	$89.25	12.488%	$100.3955	$100.40	$100.40	$100.40
Purchase #3	$99.84	12.371%	$112.1912	$112.19	$112.20	$112.20
Purchase #4	$67.82	8.258%	$73.4206	$73.42	$73.40	$73.40
Purchase #5	$128.79	8.159%	$139.298	$139.30	$139.30	$139.30
Purchase #6	$178.41	11.754%	$199.3803	$199.38	$199.40	$199.40
Purchase #7	$195.87	10.248%	$215.9428	$215.94	$215.95	$215.90
7 purchase totals =	$874.77		$968.4585	$968.46	$968.50	$968.40