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	$70.57	3.119%	$72.7711	$72.77	$72.75	$72.80
Purchase #2	$35.53	13.272%	$40.2455	$40.25	$40.25	$40.20
Purchase #3	$56.41	12.725%	$63.5882	$63.59	$63.60	$63.60
Purchase #4	$193.85	9.224%	$211.7307	$211.73	$211.75	$211.70
Purchase #5	$159.88	11.611%	$178.4437	$178.44	$178.45	$178.40
Purchase #6	$143.74	10.513%	$158.8514	$158.85	$158.85	$158.90
Purchase #7	$72.77	5.606%	$76.8495	$76.85	$76.85	$76.80
7 purchase totals =	$732.75		$802.4801	$802.48	$802.50	$802.40