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	$228.91	9.300%	$250.1986	$250.20	$250.20	$250.20
Purchase #2	$81.44	4.555%	$85.1496	$85.15	$85.15	$85.10
Purchase #3	$75.44	4.510%	$78.8423	$78.84	$78.85	$78.80
Purchase #4	$80.71	11.419%	$89.9263	$89.93	$89.95	$89.90
Purchase #5	$80.50	10.639%	$89.0644	$89.06	$89.05	$89.10
Purchase #6	$239.85	3.553%	$248.3719	$248.37	$248.35	$248.40
Purchase #7	$169.99	7.523%	$182.7783	$182.78	$182.80	$182.80
7 purchase totals =	$956.84		$1,024.3314	$1,024.33	$1,024.35	$1,024.30