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	$191.69	6.116%	$203.4138	$203.41	$203.40	$203.40
Purchase #2	$155.51	10.461%	$171.7779	$171.78	$171.80	$171.80
Purchase #3	$172.83	10.232%	$190.514	$190.51	$190.50	$190.50
Purchase #4	$122.82	3.612%	$127.2563	$127.26	$127.25	$127.30
Purchase #5	$85.56	8.183%	$92.5614	$92.56	$92.55	$92.60
Purchase #6	$231.86	9.497%	$253.8797	$253.88	$253.90	$253.90
Purchase #7	$116.82	4.756%	$122.376	$122.38	$122.40	$122.40
7 purchase totals =	$1,077.09		$1,161.7791	$1,161.78	$1,161.80	$1,161.90