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	$108.72	4.705%	$113.8353	$113.84	$113.85	$113.80
Purchase #2	$64.88	10.171%	$71.4789	$71.48	$71.50	$71.50
Purchase #3	$76.92	4.720%	$80.5506	$80.55	$80.55	$80.60
Purchase #4	$178.32	10.166%	$196.448	$196.45	$196.45	$196.40
Purchase #5	$177.60	3.686%	$184.1463	$184.15	$184.15	$184.10
Purchase #6	$88.77	12.343%	$99.7269	$99.73	$99.75	$99.70
Purchase #7	$39.63	7.821%	$42.7295	$42.73	$42.75	$42.70
7 purchase totals =	$734.84		$788.9155	$788.93	$789.00	$788.80