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	$150.28	4.249%	$156.6654	$156.67	$156.65	$156.70
Purchase #2	$86.69	3.537%	$89.7562	$89.76	$89.75	$89.80
Purchase #3	$236.82	9.588%	$259.5263	$259.53	$259.55	$259.50
Purchase #4	$201.83	4.704%	$211.3241	$211.32	$211.30	$211.30
Purchase #5	$70.59	7.516%	$75.8955	$75.90	$75.90	$75.90
Purchase #6	$190.62	10.603%	$210.8314	$210.83	$210.85	$210.80
Purchase #7	$44.94	4.867%	$47.1272	$47.13	$47.15	$47.10
7 purchase totals =	$981.77		$1,051.1261	$1,051.14	$1,051.15	$1,051.10