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	$68.38	6.544%	$72.8548	$72.85	$72.85	$72.90
Purchase #2	$95.27	11.503%	$106.2289	$106.23	$106.25	$106.20
Purchase #3	$59.82	8.474%	$64.8891	$64.89	$64.90	$64.90
Purchase #4	$163.43	3.527%	$169.1942	$169.19	$169.20	$169.20
Purchase #5	$36.38	7.413%	$39.0768	$39.08	$39.10	$39.10
Purchase #6	$174.83	6.355%	$185.9404	$185.94	$185.95	$185.90
Purchase #7	$80.84	10.391%	$89.2401	$89.24	$89.25	$89.20
7 purchase totals =	$678.95		$727.4243	$727.42	$727.50	$727.40