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	$140.42	11.614%	$156.7284	$156.73	$156.75	$156.70
Purchase #2	$97.28	4.148%	$101.3152	$101.32	$101.30	$101.30
Purchase #3	$148.94	3.805%	$154.6072	$154.61	$154.60	$154.60
Purchase #4	$179.51	9.355%	$196.3032	$196.30	$196.30	$196.30
Purchase #5	$53.47	7.728%	$57.6022	$57.60	$57.60	$57.60
Purchase #6	$219.74	9.340%	$240.2637	$240.26	$240.25	$240.30
Purchase #7	$118.66	5.680%	$125.3999	$125.40	$125.40	$125.40
7 purchase totals =	$958.02		$1,032.2198	$1,032.22	$1,032.20	$1,032.20