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	$61.46	12.715%	$69.2746	$69.27	$69.25	$69.30
Purchase #2	$240.41	6.685%	$256.4814	$256.48	$256.50	$256.50
Purchase #3	$51.78	6.297%	$55.0406	$55.04	$55.05	$55.00
Purchase #4	$40.58	5.782%	$42.9263	$42.93	$42.95	$42.90
Purchase #5	$168.67	11.772%	$188.5258	$188.53	$188.55	$188.50
Purchase #6	$163.52	13.200%	$185.1046	$185.10	$185.10	$185.10
Purchase #7	$247.63	11.573%	$276.2882	$276.29	$276.30	$276.30
7 purchase totals =	$974.05		$1,073.6415	$1,073.64	$1,073.70	$1,073.60