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	$61.39	10.712%	$67.9661	$67.97	$67.95	$68.00
Purchase #2	$99.32	3.583%	$102.8786	$102.88	$102.90	$102.90
Purchase #3	$191.59	7.856%	$206.6413	$206.64	$206.65	$206.60
Purchase #4	$57.38	13.501%	$65.1269	$65.13	$65.15	$65.10
Purchase #5	$80.67	10.187%	$88.8879	$88.89	$88.90	$88.90
Purchase #6	$209.63	12.298%	$235.4103	$235.41	$235.40	$235.40
Purchase #7	$31.78	3.507%	$32.8945	$32.89	$32.90	$32.90
7 purchase totals =	$731.76		$799.8056	$799.81	$799.85	$799.80