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	$107.74	9.573%	$118.054	$118.05	$118.05	$118.10
Purchase #2	$100.96	8.518%	$109.5598	$109.56	$109.55	$109.60
Purchase #3	$212.31	12.441%	$238.7235	$238.72	$238.70	$238.70
Purchase #4	$80.53	9.558%	$88.2271	$88.23	$88.25	$88.20
Purchase #5	$34.88	5.404%	$36.7649	$36.76	$36.75	$36.80
Purchase #6	$166.74	11.523%	$185.9535	$185.95	$185.95	$186.00
Purchase #7	$91.32	10.314%	$100.7387	$100.74	$100.75	$100.70
7 purchase totals =	$794.48		$878.0215	$878.01	$878.00	$878.10