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	$55.36	10.215%	$61.015	$61.02	$61.00	$61.00
Purchase #2	$246.59	7.701%	$265.5799	$265.58	$265.60	$265.60
Purchase #3	$6.77	4.204%	$7.0546	$7.05	$7.05	$7.10
Purchase #4	$243.97	10.430%	$269.4161	$269.42	$269.40	$269.40
Purchase #5	$171.60	6.434%	$182.6407	$182.64	$182.65	$182.60
Purchase #6	$56.31	6.450%	$59.942	$59.94	$59.95	$59.90
Purchase #7	$39.95	5.292%	$42.0642	$42.06	$42.05	$42.10
7 purchase totals =	$820.55		$887.7125	$887.71	$887.70	$887.70