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	$60.34	8.620%	$65.5413	$65.54	$65.55	$65.50
Purchase #2	$78.97	4.207%	$82.2923	$82.29	$82.30	$82.30
Purchase #3	$184.96	6.251%	$196.5218	$196.52	$196.50	$196.50
Purchase #4	$162.71	3.444%	$168.3137	$168.31	$168.30	$168.30
Purchase #5	$30.91	9.693%	$33.9061	$33.91	$33.90	$33.90
Purchase #6	$26.73	12.414%	$30.0483	$30.05	$30.05	$30.00
Purchase #7	$137.73	12.514%	$154.9655	$154.97	$154.95	$155.00
7 purchase totals =	$682.35		$731.5890	$731.59	$731.55	$731.50