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	$168.43	11.270%	$187.4121	$187.41	$187.40	$187.40
Purchase #2	$202.50	6.372%	$215.4033	$215.40	$215.40	$215.40
Purchase #3	$181.49	6.763%	$193.7642	$193.76	$193.75	$193.80
Purchase #4	$40.72	6.576%	$43.3977	$43.40	$43.40	$43.40
Purchase #5	$31.53	7.488%	$33.891	$33.89	$33.90	$33.90
Purchase #6	$138.45	3.119%	$142.7683	$142.77	$142.75	$142.80
Purchase #7	$56.81	7.224%	$60.914	$60.91	$60.90	$60.90
7 purchase totals =	$819.93		$877.5506	$877.54	$877.50	$877.60