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	$95.72	8.562%	$103.9155	$103.92	$103.90	$103.90
Purchase #2	$51.53	10.620%	$57.0025	$57.00	$57.00	$57.00
Purchase #3	$117.64	12.123%	$131.9015	$131.90	$131.90	$131.90
Purchase #4	$25.85	5.546%	$27.2836	$27.28	$27.30	$27.30
Purchase #5	$202.55	5.812%	$214.3222	$214.32	$214.30	$214.30
Purchase #6	$38.37	11.357%	$42.7277	$42.73	$42.75	$42.70
Purchase #7	$60.91	7.761%	$65.6372	$65.64	$65.65	$65.60
7 purchase totals =	$592.57		$642.7902	$642.79	$642.80	$642.70