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	$218.53	3.665%	$226.5391	$226.54	$226.55	$226.50
Purchase #2	$85.38	4.171%	$88.9412	$88.94	$88.95	$88.90
Purchase #3	$249.92	3.872%	$259.5969	$259.60	$259.60	$259.60
Purchase #4	$35.47	4.459%	$37.0516	$37.05	$37.05	$37.10
Purchase #5	$53.83	11.274%	$59.8988	$59.90	$59.90	$59.90
Purchase #6	$79.51	11.701%	$88.8135	$88.81	$88.80	$88.80
Purchase #7	$24.35	11.699%	$27.1987	$27.20	$27.20	$27.20
7 purchase totals =	$746.99		$788.0398	$788.04	$788.05	$788.00