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	$57.35	3.812%	$59.5362	$59.54	$59.55	$59.50
Purchase #2	$72.88	10.430%	$80.4814	$80.48	$80.50	$80.50
Purchase #3	$204.52	3.422%	$211.5187	$211.52	$211.50	$211.50
Purchase #4	$59.77	7.236%	$64.095	$64.10	$64.10	$64.10
Purchase #5	$46.93	3.112%	$48.3905	$48.39	$48.40	$48.40
Purchase #6	$114.69	12.338%	$128.8405	$128.84	$128.85	$128.80
Purchase #7	$139.32	13.751%	$158.4779	$158.48	$158.50	$158.50
7 purchase totals =	$695.46		$751.3402	$751.35	$751.40	$751.30