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	$156.63	6.695%	$167.1164	$167.12	$167.10	$167.10
Purchase #2	$83.88	6.455%	$89.2945	$89.29	$89.30	$89.30
Purchase #3	$209.57	10.596%	$231.776	$231.78	$231.80	$231.80
Purchase #4	$65.37	5.185%	$68.7594	$68.76	$68.75	$68.80
Purchase #5	$119.72	9.687%	$131.3173	$131.32	$131.30	$131.30
Purchase #6	$200.83	10.790%	$222.4996	$222.50	$222.50	$222.50
Purchase #7	$71.32	3.232%	$73.6251	$73.63	$73.65	$73.60
7 purchase totals =	$907.32		$984.3883	$984.40	$984.40	$984.40