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	$164.78	4.505%	$172.2033	$172.20	$172.20	$172.20
Purchase #2	$187.44	11.785%	$209.5298	$209.53	$209.55	$209.50
Purchase #3	$39.93	3.394%	$41.2852	$41.29	$41.30	$41.30
Purchase #4	$118.61	4.519%	$123.97	$123.97	$123.95	$124.00
Purchase #5	$123.41	6.869%	$131.887	$131.89	$131.90	$131.90
Purchase #6	$65.53	7.676%	$70.5601	$70.56	$70.55	$70.60
Purchase #7	$167.81	11.127%	$186.4822	$186.48	$186.50	$186.50
7 purchase totals =	$867.51		$935.9176	$935.92	$935.95	$936.00