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	$63.36	13.611%	$71.9839	$71.98	$72.00	$72.00
Purchase #2	$171.29	11.429%	$190.8667	$190.87	$190.85	$190.90
Purchase #3	$183.48	4.410%	$191.5715	$191.57	$191.55	$191.60
Purchase #4	$178.70	6.388%	$190.1154	$190.12	$190.10	$190.10
Purchase #5	$159.55	12.181%	$178.9848	$178.98	$179.00	$179.00
Purchase #6	$142.92	11.142%	$158.8441	$158.84	$158.85	$158.80
Purchase #7	$224.27	6.223%	$238.2263	$238.23	$238.25	$238.20
7 purchase totals =	$1,123.57		$1,220.5927	$1,220.59	$1,220.60	$1,220.60