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	$86.38	4.479%	$90.249	$90.25	$90.25	$90.20
Purchase #2	$100.88	6.288%	$107.2233	$107.22	$107.20	$107.20
Purchase #3	$80.74	12.404%	$90.755	$90.76	$90.75	$90.80
Purchase #4	$222.88	7.511%	$239.6205	$239.62	$239.60	$239.60
Purchase #5	$89.58	6.804%	$95.675	$95.68	$95.70	$95.70
Purchase #6	$126.26	9.244%	$137.9315	$137.93	$137.95	$137.90
Purchase #7	$99.65	12.511%	$112.1172	$112.12	$112.10	$112.10
7 purchase totals =	$806.37		$873.5715	$873.58	$873.55	$873.50