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	$85.85	11.466%	$95.6936	$95.69	$95.70	$95.70
Purchase #2	$162.38	12.840%	$183.2296	$183.23	$183.25	$183.20
Purchase #3	$131.64	6.693%	$140.4507	$140.45	$140.45	$140.50
Purchase #4	$5.42	8.233%	$5.8662	$5.87	$5.85	$5.90
Purchase #5	$54.83	4.285%	$57.1795	$57.18	$57.20	$57.20
Purchase #6	$178.28	7.287%	$191.2713	$191.27	$191.25	$191.30
Purchase #7	$127.36	11.281%	$141.7275	$141.73	$141.75	$141.70
7 purchase totals =	$745.76		$815.4184	$815.42	$815.45	$815.50