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	$191.80	12.556%	$215.8824	$215.88	$215.90	$215.90
Purchase #2	$35.89	12.542%	$40.3913	$40.39	$40.40	$40.40
Purchase #3	$184.37	6.799%	$196.9053	$196.91	$196.90	$196.90
Purchase #4	$240.43	11.601%	$268.3223	$268.32	$268.30	$268.30
Purchase #5	$223.57	11.190%	$248.5875	$248.59	$248.60	$248.60
Purchase #6	$11.55	6.817%	$12.3374	$12.34	$12.35	$12.30
Purchase #7	$109.94	4.565%	$114.9588	$114.96	$114.95	$115.00
7 purchase totals =	$997.55		$1,097.3850	$1,097.39	$1,097.40	$1,097.40