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	$69.85	4.115%	$72.7243	$72.72	$72.70	$72.70
Purchase #2	$58.62	7.372%	$62.9415	$62.94	$62.95	$62.90
Purchase #3	$205.86	4.601%	$215.3316	$215.33	$215.35	$215.30
Purchase #4	$175.85	8.492%	$190.7832	$190.78	$190.80	$190.80
Purchase #5	$60.81	4.164%	$63.3421	$63.34	$63.35	$63.30
Purchase #6	$241.32	9.620%	$264.535	$264.54	$264.55	$264.50
Purchase #7	$204.95	7.840%	$221.0181	$221.02	$221.00	$221.00
7 purchase totals =	$1,017.26		$1,090.6758	$1,090.67	$1,090.70	$1,090.50