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	$121.76	4.780%	$127.5801	$127.58	$127.60	$127.60
Purchase #2	$200.82	10.556%	$222.0186	$222.02	$222.00	$222.00
Purchase #3	$61.92	3.268%	$63.9435	$63.94	$63.95	$63.90
Purchase #4	$115.90	6.219%	$123.1078	$123.11	$123.10	$123.10
Purchase #5	$129.91	4.309%	$135.5078	$135.51	$135.50	$135.50
Purchase #6	$139.61	7.786%	$150.48	$150.48	$150.50	$150.50
Purchase #7	$97.69	4.803%	$102.3821	$102.38	$102.40	$102.40
7 purchase totals =	$867.61		$925.0199	$925.02	$925.05	$925.00